· preface. in the following pages methods for complete an alyses are outlined, and substances...

A COURSE lN

QUANTITATIVE CHEMICALANAL"SIS

GRAVIMETRIC AND VOLUMETRIC

B"’

NICHOLAS KNIGHT, A .M ., PH.D .

Profwsor of Chem istry Corneil CollegeMount Vernon, Iowa

REVISED EDITION

NEW "ORK AND CHICAGO

m) : a. 9. fl ames t ompanp

1915

PREFACE.

IN the following p ages methods for complete an

alyses are outlined, and substances have been se

lected for analysis which, it is believed, will illustrate the more common methods of separating and

determining the parts of a compound or mixtures ofcompounds . In some determinations, two or more

methods are outli ned. In other cases, even thoughonly one process is suggested, it should be borne inmind that there is often a choice of several methods,and the same result can often be attained in many

different ways .

The larger works should be freely consulted bythe student that he may become acquainted with thevariety of processes that are more or less in common

use . The work is graduated, and both in the gravi

metric and volumetric divisions proceeds from sim

p ler substances and operations to the more complex .

The arrangement is such that any part may be om it

ted to suit the time and convenience of the student.

The ionic theory is now quite generally em ployedto explain chemical reactions . The theory is usually

studied in the courses in general chemistry,and it

has not been deemed necessary to introduce the sub

rJcet he e NICHOLAS KNIGHT .

CORN ELL COLLEGE,

June, 1915.

CONTENTS.

PAGE

PREFACE

PART I

INTRODUCTION

The Care of the Balance

Weighing

PrecipitatesFiltering and Washing

Preparing the CruciblesDesiccators

Evaporation

The Care of Platinum

Distilled Water

Cleanliness and Carefulness .

PART II

GRAVIMETRIC ANAL" SIS

Filter Papers

I . To Analyze a Silver CoinII . Potassium Bichromate

CONTENTS

III . Magnesium Sulphate

IV. Copper Sulphate

V. Barium Chloride

VI . Iceland SparVI I . Dolomi te

VII I . SideriteI" . Chalcopyrite" . Sodium Phosphate

" I. German S ilver" II. Smaltite" I I I . Fahlerz

" IV. Phosphorite (Apatite)

"V. Granite

PART III

VOLUMETRIC ANAL" SIS

Indicators

General Remarks and SuggestionsTitration with Potassium Perm anganate

Titration with Potassium Bichromate

Titration with Silver NitrateAlkalimetry

Acidimetry

Iodimetry

CONTENTS vii

PART IVPAGI

Tm : ANAL"SIS or ORD INAR" DRINK ING WATER 119

PART V

APPENDI"

Reactions

The Weight of a Volume of GasThe Weight of a Litre of Different Gases

Under Normal Conditions, and the Densi

ties Referred to Air

Tension of Water VaporInternational Atomic Weights

Index

PART I

INTRODUCTION

PART I .

INTRODUCTION.

The Care of the Balance.

THE balance should be kept, if possible, in a welllighted room on the north side of a thick-walledbui lding, where the temperature is constant. It

should not rest against an outer wall. The roomshould be protected from laboratory fumes . Thebalance support should be firm, to avoid ordinaryj ars .

The sensitiveness of the balance depends largelyupon the sharpness of the knife edge on which thebeam rests when swinging. Therefore release and

arrest the beam with a slow and steady movementof the hand

,as j erky movements inj ure knife edges .

Arrest the beam only when it is in a horizontal posi

tion. A balance with agate knife edges and planesis to be p referred .

D o not allow the pans to rotate in a horizontal

direction . This causes a knife edge to scrape on itssupport .

Arrest both beam and pans before placing anything on the pans or removing anything from them.

8

4 QUANTITATIVE CHEMICAL ANALYSIS

A small dish of calcium chloride should remain inthe balance case to dry the air .

Weighi ng.

S it directly in front of the centre of the balanceto avoid parallax .

Carefully remove the dust from the pans with a

camel ’s-hair brush before beginning to weigh.

See that the balance is level . Determine the zeropoint by observing the swings of the pointer . I f adj ustment is necessary call on the one in charge of

the laboratory.

Place the obj ect to be weighed in the centre of theleft-hand pan and the larger weights in the centre

of the right. The tenths and hundredths follow in

separate rows in the order in which they are taken

from their positions .

Weighings should be made with the balance caseclosed .

Hot obj ects cannot be correctly weighed, owing tothe upward draughts they create about the pans .Metallic substances should be weighed on a small

watch-glass,and no obj ect to be weighed should be

placed directly on the scale pan .

Ascertain the weight of the obj ect by the vacantplaces in the box

,and veri fy when the weights are

returned . A neglect of this will often occasion serious error in an analysis .

The m ost full and clear directions that can be

INTRODUCTION 5

given wi ll not take the place of the competent instructor, who should frequently be consulted by thestudent, especially in the beginning of the course .The substance prepared for analysis should

usually be contained in a weighing bottle . The hottle and contents together should be carefully weighed

,

the required amount, generally a gram, withdrawn,and the bottle and contents again weighed . The

difference is the amount of the substance taken .

When the weighing is completed do not neglectto close the balance case and to place the cover on

the weight box .

Precipitates.

Substances are usually best precipitated in a clean,transparent beaker glass, where the phenomena aremore easily observed . The beaker should be coveredwith a watch-glass when solutions are made and sub

stances precipitated in which there is an evolution ofgas . Any accumulations on the watch-glass shouldbe carefully rinsed into the beaker. The size of thebeaker should correspond to the amount of the sub

stance it is to contain . (Loss is inevitable from asmall solution and precipitate in a large vessel. ) Toomuch of the reagent is to be avoided, as some p recip itates are soluble in an excess . To allow certain precip itates to become crystalline, or to collect in aggre

gates,which renders them less likely to go through

the paper, they should stand a number of hours be

6 QUANTITATIVE CHEM ICAL ANALYSIS

fore filtering. In general, the reagent should be

slowly added while stirring the contents of the

dish, to prevent the carrying down of other sub

stances .

Fi ltering and Washing.

A filter paper of a size corresponding to the

amount of the precipitate should be chosen . The

ability to do this can be acquired by a little practice .

A paper unnecessarily large requires more washwater, and this involves loss of time in cases where

the filtrate must be condensed for subsequent workupon it ; besides, as all precipitates are more or lesssoluble in water

,it is on this account desirable to use

no more in washing than necessary . If the filter is

too large,more of the substance will remain up on it

on removal for ignition,which interferes with the suc

cess of the work . The paper should be folded to fit

perfectly the sides of the funnel,above which it

should not proj ect. It should be moistened with distilled water before beginning the filtration . The

liquid should first be poured through the paper without stirring up the p recipitate from the bottom . By

this means the pores are filled, and fine precipitates

are not so likely to go through . Grease the edge ofthe beaker (p lain beakers are recommended) with asmall quantity of vaseline, and always transfer the

substance to the filter by allowing it to flow down a

glass rod . The stem of the funnel should touch the

INTRODUCTION 7

side of the receiving vessel to avoid loss by spatter

ing. Substances can be removed from the sides ofthe containing vessel by a stiff feather properlytrimmed, or by a piece of rubber tubing stretchedover a glass rod . In filtering, the paper should befilled no nearer the top than four millimetres .The precipitate can usually be washed with hot

water, which more quickly accomplishes the obj ect.*

Exceptions are sometimes fine precip itates like barium

sulp hate, which easily go through the filter,and those

soluble in hot water or oxidized by it. Twelve tofifteen washings are generally sufficient, but no rulecan be given . A safe way is to test about a cubiccentimetre of the filtrate with a suitable reagent, or

to evaporate a few drops to dryness on a platinumfoil. It is well to collect the washings in a separate

beaker, as precip itates will sometimes go throughthe filter when the wash water is app lied .

A vacuum pump can often be employed to advan

tage in filtering, in which case a platinum cone isnecessary for the support of the paper . Care must

be exercised that the filter be not rup tured . When

the precip itate cracks, it must be pressed togetherwith the glass rod used in filtering to insure thorough

washing.

The internal friction of water at 100° is less than one

six th of the friction at


Preparing the Crucibles.

The crucible, whether of porcelain or platinum,

should usually have a cap acity of l 5cc After

washing with distilled water, it is heated about tenm inutes in the Bunsen flame . The lid should be so

adj usted as to cover one-half the mouth of the cru

cible, which should slant 45°

from a vertical

position . (Fig. It should be cooled in the air

to about when i t is placed in the desiccatorand weighed after about fifteen minutes . It is again

heated, cooled, and weighed as before until constantweight is secured, or until two weighings do not varym ore than gram . Two crucibles can beheated and cooled at the same time .

Burning the Filter and Heating the Precip itate.

Remove the water from the stem of the funnelwith a small strip of filter paper, and cover them outh of the funnel with a piece of moistened filter

pap er to protect the precipitate from dust. The

precipitate should be thoroughly dried in the air

bath . Meanwhile other work can be in p rogress, so

that time need not be lost. Above a Sheet of glazedpaper spread -upon the table, and held firmly by an

iron weight on one corner (light-colored paper fordark precipitates and vice versa) , rem ove the p recipitate as thoroughly as possible to a weighed pot ce

Many substances are reduced by the burning p aper whichare not subsequently ox idized when heated. It is, therefore,

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lo QUANTITATIVE CHEMICAL ANALYSIS

glazed p aper. Fold the filter three or four times,wrap it loosely with a piece of platinum wire, ignite

the tip with the Bunsen flame, and hold the burning

paper j ust above the crucible . Again, with the

camel ’s-hair brush transfer any residue on the glazedpaper to the crucible . Then heat the crucible in thetip of the Bunsen flame, at first carefully and withthe cover on, lest any moisture in the precipitate oc

casion loss . Finally heat to a dull redness with

the cover removed or so placed as to allow a free

access of air. Let cool to about Trans

fer the crucible to the desiccator,and after stand

ing fifteen to twenty minutes in the balanceroom it can be weighed . Repeat the heating untilconstant weight is secured . Deliquescent substancesand those that absorb carbon dioxide from the airmust be weighed as rap idly as possible . Porcelaincrucibles answer for most purposes equally as wellas the more expensive platinum. They should becleaned, heated, and weighed after each analysis .

Desiccators.

There are many convenient forms in common use.

The bottom should contain a layer of fused calciumchloride, about an inch in depth . For some purposes,concentrated sulphuric acid or pumice stone saturatedwith sulphuric acid is a more suitable drying material. The crucible can rest in a pipe-stem triangle.

This is ignition or igniting the p recip itate.

INTRODUCTION 11

The desiccators should be kept covered when not inuse to prevent the deterioration of the drying agent.

Evaporation.

This usually proceeds in a porcelain dish on thewater-bath . During the operation, a funnel should

be used to protect the di sh and contents from dust.A solution can be quite rap idly concentrated in aflask

,inclined at an angle of heated with a free

flame, and som etim es this method can be emp loyed .

The flask at the beginning should not be more thanhalf full . Pieces of glass rod, or a small roll of

platinum wire,can be inserted in the liquid to avoid

bumping. It should be remem bered that hot alkalis

dissolve the silica of glass, which m ight interfere

with the analyses. Porcelain dishes are less easily

attacked than glass .

The Care of Platinum .

In these times when platinum i s so expensive, it

seems necessary to take every p recaution to prolong

the li fe of each article used .

Platinum app aratus should be frequently scoured

with fine,m oistened sea sand . Heat tends to crys

tallize the surface of platinum ,and the crystalline

structure gradually penetrates the dish . Abradingthe surface rem oves the crystals and renders theplatinum usable for a longer period .


Liquids containing free chlorine or aqua regiashould not be introduced into platinum vessels onaccount of the solvent action .

Caustic alkalis attack platinum ; fusion with thesecan be made in silver

,iron, or nickel dishes .

The shape of platinum vessels should be preserved, and the edges should not be bent.The stains of iron and other substances can often

be removed by placing p owdered acid potassium sul

phate in the vessel and heating. It should not be so

strongly heated as to change all the acid sulphateto the normal sulphate ; the latter expands so rapidlythat it might break the platinum dish.

Disti lled Water.

An abundance of distilled water should be available in all quantitative work. This should occas ionally be tested to learn i f any residue remains onevaporation. It is frequently stored in glass bottlesor carboys, but ordinary glass is appreciably solublein distilled water. Dishes, before they are used,should be washed with distilled water and it shouldalways be employed in washing precipitates .

Cleanliness and Carefulness. Records.

These conditions are sometimes overlooked, butthey are essential to the highest success in this work .

Whenever a piece of apparatus has been soiled by

INTRODUCTION 18

use, it should be thoroughly cleaned . Before using,it should be rinsed with distilled water. Apparatus

should not be allowed to accumulate on the desk,but should be returned to its appropriate place. Thedesk should always be scrupulously clean.

The utmost care should be exercised in all details

of the work. The student must be constantly on thealert to avoid everything that would mar his results .

The habits that can thus be acquired are invaluable .Before beginning an analysis, the general methodshould be well in mind. It is only in this way that

the time can be well filled up and m any mistakes

avoided . The reason for each step should be clearlyin the mind before taking it.An analysis, or a portion of it, should be repeated

if a correct result is not gained . This should always

be done when the source of the error has escapedobservation .

After some practice, two analyses can be carriedon at the same time . Everything should be accurately labelled to avoid mistakes .

The student should form the habit of keeping aneat and busines s-like record of everything done.

Two note-books should be employed,— one to be

kept in the laboratory for the daily records ; theother to be written up more leisurely . Mistakes

made and difficulties encountered should be carefullyrecorded . All weights should be entered in the notebook and never on loose sheets of paper .

ART II

GRAVIMETRIC ANAL" SIS


acid to ten of water) , and wash for the same lengthof time in a stream of running water . Finally

,wash

si x or eight times in distilled water,thoroughly

draining off the water each time . Place these between sheets of filter paper and allow them to dry in

a steam-bath for two or three days . They are conven iently kept in round boxes of suitable size .

Ignite ten filters of each size, one at a time, se

lected from different p laces in the pile, wrapping

each loosely with a piece of platinum wire. Collectthe ashes of each ten in a weighed porcelain crucible,heat to dull redness, cool in the desiccator, andweigh . Thus the weight of a filter ash is deter

mined,which must always be deducted from the

weight of the precipitate .

I. To Analyze a Silver Coin.

Composition : si lver,copper, and tin .

Carefully clean with a little moist sea-sand a

five-cent silver coin or the half of a ten-cent coin .

Weigh on a watch-glass, transfer to a sm all beaker,and add two p arts of distilled water and one of pure

nitric acid . There should be about of the liquid .

Cover with a watch-glass, and dissolve by gentlyheating with a small flam e.

*

The tin,which is sometimes present in the coin as

an impurity in the COp p er, separates as a few dark

The student should write all the reactions that occur inthe analyses.

GRAVIMETRIC ANALYSIS 19

scales of on the bottom of the beaker .Rinse the accumulations on the watch-glass into thebeaker.

l . TIN— Filter the solution to collect the tin .

Wash the precipitate thoroughly with hot water.Remove the precipitate with the filter ashes to aweighed porcelain crucible

,and heat to redness until

constant weight is secured . Sn (Ol-l ) 4 Sno2

2H20 . From the amount of tin oxide the percentage

of tin can be determined .

2. SILVER— Gently heat the filtrate from 1toboiling. Then with constant stirring cautiously adddilute hydrochloric acid Tuntil no further precipita

tion takes place . Press the precipitate with a glass

rod to expel the liquid from it. Filter,and wash with

hot water.

3. The excess of HCl that was added to 2 dissolves a small quantity of silver chloride. Therefore

evaporate the filtrate from 2 to dryness on the water

bath, add a few drops of dilute nitric acid, I a littlewater, and a few drops of dilute hydrochloric acid .

Filter,and wash the precipitate with hot water .

4. COPPER— Warm the filtrate from 3 in a poreelain dish On the water-bath. Add a strong solution

of caustic potash to slight alkalinity . Let stand for

ten minutes on the water-bath and filter with the

Chem ically pure cop per can be obtained only by elec

trolysis.

1' One p art concentrated Hcl and one p art water.1One p art HNO3 and one p art water.


pump . The black precipitate is cupric oxide (CuO ) .

Test the filtrate with a few drops of yellow ammonium sulphide to learn if the copper is all p recip itated . Wash the precipitate with hot water unti lthere is no longer an alkaline reaction . Treat the

precipitate in the usual way . From the cupric oxidedetermine the amount of copper .To determine the percentage of silver1. Remove the precipitates from the filter papers

to a weighed porcelain crucible . Heat gently until

the silver chloride begins to melt. Cool, and transfer

to the desiccator .*

2. Weigh a crucible and a piece of platinum

wire together, then burn the two filter papers fromthe preceding operation . The burning paper reduces

the small amount of silver chloride to metallic silver . 'l

' Some silver will also form an alloy with theplatinum. The silver thus obtained added to the

amount in the chloride is the total silver in the coin .

To prepare the caustic potash for use in these

analyses : To 700cc of absolute alcohol in a glass

stoppered bottle, add 250g commercial caustic potash .

Shake the bottle until all the solid has dissolved .

Filter the solution into a silver dish . Evaporate the

filtrate with the free flame cautiously,lest the alcohol

Finally, rem ove the chloride from the crucible by addingzinc and dilute hydrochloric acid.

1‘ 4AgCl C 21120 4Ag CO

24HC].

Pap er


take.

fire . Toward the end of the evaporation, a dark

scum collects on top . This is aldehyde resin . It is

produced by the action of the hot alkali on aldehyde,a little of the latter being formed by the oxidation of

the alcohol . Remove the scum with a silver spoonand continue the evaporation unti l a drop of the

liquid placed upon a porcelain plate instantly hard

ens and becomes white and opaque . Place the silverdish in a vessel of cold water until the substance

hardens . Remove the cake,place it between filter

papers,break it into small pieces with a mallet, and

put away in a well- corked bottle .

The analysis of a silver coin resulted

Total

Remarks.

1. The ashes of the filter papers from the

silver chloride may be collected in a separate,weighed crucible

,and the metallic Silver changed to

silver chloride . The platinum wire is wound around

the tip of the filter papers, or where there is the least

amount of adhering chloride . The residue is moist

ened with a few drops of nitric acid, and then witha few drops of hydrochloric acid . The substance is


then evaporated to dryness and ignited with the

Bunsen burner to expel any m oisture . It is then

weighed as silver chloride and the am ount is addedto the main portion .

2. The silver chloride or any silver halide,and many other precipitates may be collected

in a weighed Gooch crucible, and the moist

precipitate heated as usual. The Gooch cruciblemay be of porcelain or platinum . It is a crucible of

the ordinary size, with a perforated bottom, which

should be covered with a layer 2m m thick, of fine

asbestos . The asbestos should first be boiled in dilute

hydrochloric acid and afterwards well washed indistilled water .

11. Potassium Bichromate.

Composition : K20 (Cr0 3 ) 2 .

Weigh four grams of the pure,

finely pulverized

substance in a small porcelain evaporating dish .

With a sm all flame heat the powder without meltingit,constantly stirring with a glass rod, to expel all

the moisture . This is accomplished when the powderno longer adheres to the rod .

Transfer the dry bichromate to a clean, dry weigh

ing bottle or test-tube . Weigh a gram into a flask

of 200cc capacity, to which add 50cc of dilute hydrochloric acid . Place a small funnel in the mouth of

the flask,incline the flask at an angle of and

heat with a small flame until about half the liquid has


evaporated . This treatment changes the original substance into potassium and chromic chlorides ahd abright green color is obtained.

Transfer the chlorides to a porcelain evaporatingdish, warm on the water-bath, and add ammonia toslight alkalinity . This forms chromic hydrate. Continne to heat on the water-bath until all ammonia hasbeen driven ofi

,

* adding distilled water from time to

time if necessary .

1. CrOS— Filter with the pump . Wash with hot

water . Remove the precipitate from the paper to aweighed porcelain crucible, burn the paper, add theashes to the crucible, which is heated to dull redness ,until constant weight is attained . This gives Cr20 3,

from which CrO3 is easily determined.

2. K20— Evaporate the filtrate from 1in a plati

num evaporating dish to dryness on the water-bath .

Rem ove the dish, and heat with a Bunsen flame, be

ginning at the rim and gradually heating toward the

bottom to drive 0 3 all the ammonium chloride . It

can be heated to dull redness without volatilizing thepotassium chloride . A black residue will sometimesappear in the dish . This is organic impurity contained in ammonia, and it must be removed . Dis

solve the substance in a very small quantity of warm

water, stirring with the finger . Filter through a

small paper into a weighed platinum crucible . Washwell with hot water and evaporate to dryness on the

Chrom ic hydroxide is som ewhat soluble in dilute em

monia.


water-bath. Heat the crucible to dull redness,cool

,

and weigh as usual . From the amount of potassium

chloride obtained, the percentage of K20 can be

com puted .

An analysis resulted

III . Magnesium Sulphate. MgSO 7H20 .

Pulverize five or Six grams of the chemically pure

substance and transfer to a weighing bottle. Weigh

out three one-gram portions,— one gram in a weighed

porcelain crucible for the water determination,one

gram in a small beaker for Mgo, and one gram in a

small beaker for $0 3 .

1. To determ ine the percentage of waterPlace the crucible before mentioned about twenty

inches above a very small flame and heat for twentyminutes . Then lower the crucible an inch and leave

for seven or eight minutes . Continue lowering an

inch and leaving seven or eight minutes each time,until the crucible has nearly reached the flame .

Raise the crucible a few inches and cautiously heatwith the Bunsen flame. TOO great heat would decompose the magnesium sulphate, and the gradual

heating is necessary to avoid loss. Cool in the desic

QUANTITATIVE

H20

SO,

MgO

Total

Remarks.

1. Barium sulphate often comes down as a

very fine precipitate,and is diflicult to filter . By

adding hot barium chloride to the hot solution of

sulphate,the finer particles are dissolved and add

themselves to the coarser particles ; also when precip itated hot, there is a tendency for the barium sul

phate to crystallize, and therefore, it is less likely togo through the pores of the filter paper. To heat

the precipitated substance two or three times to theboiling point, with constant stirring, also increasesthe size of the particles and makes the filtration aneasier process .

2. It sometimes happens that a result too high in

magnesia is obtained . This may be due to imperfect

washing,or to the form ation of another salt (NH, ) 4in connection with the ideal phosphate,

MgNH4PO4 . Similarly,a high result may be oh

tained in precipitating phosphoric acid with mag

nesia mixture. In all cases, the remedy is to dissolve the precipitate in hydrochloric acid, add a fewdrap s of the precipitant, disodium phosphate, or

magnesia mixture, and ammonia in considerableexcess .

CHEMICAL ANALYSIS

GRAVIMETRIC ANALYSIS

Before proceeding with minerals which are moreor less complicated in structure

,the analysis of two

additional simple salts is here suggested . These may

be om itted by any who seem to have had sufi cient

practice from the analyses before indicated.

IV. Copper Sulphate. 51120 .

Weigh a gram of the pulverized substance into aweighed porcelain crucible for the water determina

tion,a gram in a porcelain evaporating dish for

the CuO,and a gram in a small beaker glass for

SO,.

1. Determine the water by heating the crucibleand its contents in an air-bath at 200

°

—250°

to con

stant weight .

2. The SO, is determined as in magnesium sulphate .

3. The CuO i s precipitated on the water-bath with

a solution of caustic potash, as in the silver coin .

Copper sulphate is frequently associated with

ferrous sulphate,from which it can hardly be sepa

rated even by repeated crystallization . It can be

purified as follows : one hundred grams of the comm ercial article is dissolved in water and filtered . It

is then heated to boiling, and the iron is oxidizedwith —10"c of nitric acid . Pure copper sulp hate

will then crystallize from the concentrated solution .

The salt should be thoroughly dried between filter

papers and kept in a glass-stoppered bottle .


V . Barium Ch loride. BaCl 2H20 .

Weigh a gram of the pulverized salt in a crucible

for the water determination, and a gram in each of

two small beakers for the barium and chlorine determ inations .

1. Determine the water as in magnesium sulphate .2. BARIUM- Precip itate the hot solution of barium

chloride as sulphate with dilute sulp huric acid*

from the amount of the barium sulphate, com p ute

the percentage of barium .

3. To determ ine the chlorine .

Add 5cc nitric acid to the substance in solutionand p recipitate the chlorine with silver nitrate. De

term ine similarly to the method em ployed in esti

mating the silver of the coin . D o not add the ash

from the paper to the precipitate of silver chloride .

VI. Iceland Spar.

Composition : CaO, CO2, and sometimes SiOz.

In the analysis of a m ineral, about twice as muchof the substance should be pulverized as is likely to

be required . This amount permits repetition of parts

of the work,when necessary . An agate mortar

should be used in the preparation of the powder,which should be so fine as not to feel gritty when

placed between the teeth . A mineral is frequently

not homogeneous, and the powder should be thor

oughly mixed before beginning the analysis .

One volum e of strong acid in Six volum es of water.


Select a clear crystal of Iceland spar and pulverize four grams .1. To determine SiO,,

if present .

Weigh a gram of the powder in a small beaker,add

60cc dilute hydrochloric acid (one part acid, fourparts water) , covering quickly with a watch-glass .After the substance is dissolved

,heat to boiling, and

continue the heat for one or two m inutes to remove

the CO2. R inse the watch-glass into the beaker. If

S iO2 is present, after standing a short time, it can

be. detected with a glass rod as a gritty residue on,

the bottom of t he beaker . Filter,wash with hot

water, and transfer to a weighed crucible . Heat,and determine in the usual way .

2. To determine the CaO .

Add ammonia to the filtrate from 1to slight alkalin ity . Heat to boiling, and precipitate the calcium

as oxalate with ammonium oxalate . Let stand a fewhours and filter .

Transfer the dry precipitate to a weighed platinum

crucible and change to calcium sulphate . This is ac

compli shed by adding to the precipitate six or eight

drops of cone. sulphuric acid and heating with a

Bunsen flame underneath and one above the crucibleuntil fumes of SO

,no longer escape . Continue the

treatment,adding more drops of sulphuric acid, until

up on heating constant weight is attained . The per

centage of calcium oxide can be determined from theamount of calcium sulphate .

3. To determine the CO,.


Bunsen’

s method is recommended . (Fig. Theapparatus is inexpensive and can be obtained fromthe usual dealers . The hydrochloric acid employedin the carbon dioxide determinations should consistof four parts of water to one of strong acid .

A gram of the fine powder is weighed into theflask

,d. The bulb, c, is nearly filled with the dilute

hydrochloric acid . The bulb, e, contains cotton, whichassists in condensing and absorbing the m oisture .

Attached to the bulb is a small tube, f, filled with

fused calcium chloride . The apparatus from c to f,inclusive, is carefully weighed before and after theoperation . After the first weighing, with a smallrubber tube and the mouth, the acid is brought intod. When efiervescence has ceased, the solution isheated to 70

°

to expel the CO, . By means of the

aspirator, H, air is drawn through the apparatus for

fifteen minutes, further to remove the CO,. The

flask, d, is in a beaker of cold water, while the air isaspirated through . It is weighed

,heated as before,

and air drawn through to constant weight, or untiltwo successive weighings difl'er by no more than 2m8From the loss of weight

,the percentage m ay be

calculated.


CaO

SiO2

CO2

Total


VII. Dolom ite.

Composition : chiefly calcium and magnesium carbonates, with ferrous carbonate, ferric oxide, andsilica and sometimes m anganese .1. To determine C0 2 .

Proceed as in the case of Iceland spar . When the

acid i s in contact with the powder it must be slightlywarmed to efiect solution .

2. S iO, .

To a gram in a porcelain evaporating dish,add

dilute hydrochloric acid and cover with a watch-glass .

Warm on the water-bath until all evolution of gas has

ceased . R inse the contents of the watch-glass intothe dish and evaporate on the water-bath until crystals begin to appear . Then as the drying continues,stir the substance constantly with a glass rod, untilthoroughly dry, and a fine powder remains . Moisten

the powder with a few drops of concentrated hydrochloric acid

,then with about 20cc of dilute hydro

chloric acid and the same quantity of water . Filter

while warm . Dry, and ignite the precipitate, whichis mainly SiO,

.

3. FeO .

*

To the filtrate from 2 add a few drops of fumingnitric acid and heat to boiling to oxidize the iron .

Add two grams of ammonium chloride to prevent a

precipitation of magnesium . Precipitate the iron

If m anganese is p resent, the iron and m anganese shouldbe determ ined as in Siderite, q. 0 .


weighed as usual . It is then moistened with a fewdrops of dilute sulphuric acid

,and the crucible

nearly filled with a solution of hydrofluoric acid . Iti s evaporated to dryness on the water-bath

,ignited,

and weighed . The silica is volatilized by the treat

ment, and the amount is represented by the loss in

weight. The residue,consist ing principally of iron

and alum ina, is rem oved from the crucible with

warm , dilute hydrochloric acid, diluted to a suitable

volume,and the small amount of platinum which was

dissolved by the hydrofluoric acid is precipitated withhydrogen sulphide . The precipitate is discarded

,

and after heating the filtrate to rem ove the excess ofhydrogen sulphide, it is added to the main filtrate .

2. Sometimes a second evaporation of the first

filtrate will give another residue containing silica,which is to be added to the main portion ; and oftensilica will remain in solution to be precipitated withthe iron and alumina ( should the latter be present) .

The dried iron and alumina precipitate is fused

with acid potassium sulphate, as in the estimation of

titanium oxide,page 72 . The fused mass is ex

tracted with water,evaporated nearly to dryness in a

porcelain dish, and 25“ concentrated sulphuric acid

are added . It is heated with the free flam e while

copious fumes of SO, escape . Water is added to the

porcelain dish and the precipitated silica is removed

by filtration .

3. Dolom ites may also contain alumina, whichwould be precipitated with the iron . These can al


ways be separated and determined as described inthe analysis of phosphorite, and also as follows :

The well-washed, moist precipitate of iron oxide and

alumina is dissolved in warm, dilute hydrochloricacid and evaporated in a porcelain dish nearly todryness to remove most of the hydrochloric acid . An

excess of a solution of caustic potash is then added,and it is left fifteen minutes on the water-bath . This

precipitates the iron and leaves the alumina in solution as potassium aluminate. Filter and wash the

precipitate of iron with hot water. The iron cannotbe thoroughly freed from the caustic potash by washing. Therefore, dissolve the moist precipitate of ironwith warm , dilute hydrochloric acid, heat to boi ling,and precipitate the iron as usual with amm on ia .

Filter and dry the precipitate, which, on ignition, becomes FezO,

.

AlzO,

. The first filtrate from the iron is acidifiedwith hydrochloric acid

,heated to boiling, and ren

dered alkaline with a slight excess of ammonia . The

ignited precipitate is AlzO,.

4. Ammonium chloride prevents the precipitationof magnesium . The ammonia tends to precipitate them a g n e s i u m :

2NH4CI. But the reaction is reversible, and the

tendency is strongly in the reverse direction in presence of an excess of ammonium chloride : Mg(OH)2NH

4CI MgCl2 QNH4OH.

Dolomites and lim estones m ay contain sul

phates. These are determined as follows : A portion


of the rock powder is dissolved in hydrochloric acid,and the insoluble portion is removed by filtration .

The filtrate is heated to boiling and the sulphate isprecipitated with hot barium chloride solution . In

soluble sulphates like barium and strontium sulphateswould be contained in the first precipitate, and their

determ ination would require special treatment by fusion in a platinum crucible with sodium carbonate .6. In precipitating calcium with ammonium oxa

late, a small amount of magnesium may also be pre

cip itated as oxalate . To separate these, the p recip i

tate is dissolved in warm,dilute hydrochloric acid,

and the solution is rendered alkaline with amm onia .

This precipitates the calcium and leaves the magnesium in solution . The filtrate from the calcium isadded to the main filtrate containing the greater part

of the magnesium,and the whole is precipitated as

indicated, with disodium phosphate and a considerable excess of ammonia . When the magnesium content is relatively small the double precipitation is

not necessary .

VIII . Siderite.

Composition : Principally ferrous carbonate,to

gether with ferric oxide,Silica

,and m anganese, cal

c ium and magnesium carbonates .

1. To determine the C0 2. Proceed as before .

2. To determine the SiO,. Proceed as with

dolomite .

3. To determine the total am ount of iron .


To the filtrate from 2, which should be containedin a beaker of 750“ capacity, add drop by drop fuming nitric acid until the dark coloration noticed atfirst disappears and the solution is yellow. Heat to

boiling, and cool in a vessel of water . Add more

nitric acid . I f there is no change of color,the iron

is completely oxidized . Heat to boiling, and neutralize the acids with crystals of sodium carbonate . A

watch-glass must be kep t on the beaker during theevolution of CO2 to

'

avoid loss, and the liquid should

be heated to the boiling point in the entire process ofneutralization . When exactly neutral

,precipitate the

iron with barium carbonate . An excess of this re

agent does no harm . Filter with the pump and washwith hot water .Then as completely as may be, without injury to

the filter, with a trimm ed feather transfer the p recip i

tate to the same beaker that was used in the neutralization . Add dilute hydrochloric acid to the p recip itate and boil until all is dissolved . The solution now

doubtless contains an excess of the acid . Therefore

p our the solution through the sam e filter paper to

dissolve the residue upon it. Wash with hot wateruntil the paper is white . Heat the filtrate to boilingand precipitate the barium with dilute sulphuric acid .

Let stand twenty-four hours and filter . The p recip i

tate need not be saved . Heat the filtrate to boiling

and precipitate the iron with amm onia . Filter withthe pump . When ignited

,the precipitate becomes

PezO,.


4. After acidifying the filtrate from 3 with hydrochloric acid

,concentrate it in a flask . Transfer the

substance to a beaker and remove the barium withdilute sulphuric acid .

5 . MnO .

Concentrate the filtrate from 4 to 25“ Make

it alkaline with amm onia and add an excess of ye]low ammonium sulphide . Let stand eighteen hours .

Filter,and wash the precipitate with cold water

that is slightly colored with the amm onium sul

p hide Place the filter containing the substance

over a p orcelain evaporating dish, and using a

watch-glass,as there is an evolution of sulp hu

retted hydrogen, add warm , not hot, dilute hydro

chloric acid . Thoroughly wash the filter with hot

water .Leave the filtrate twenty minutes on the water-bath

to allow the sulphuretted hydrogen to pass ofl'

.

Should sulphur separate out, which som etimes happens, filter to remove it. Precip itate with sodiumcarbonate to alkaline reaction . Let rema in fifteen

minutes on the water-bath to remove the carbon dioxide . Filter with the pump . When strongly heated,the p recipitate becomes Mn

,O,, from which the MnO

can be calculated .

6. CaO .

Concentrate the filtrate from 5 on the water-bathand filter to rem ove any sulp hur . Precipitate the

calcium as oxalate . As the quantity is usually sm all,the dried precipitate can be transferred to a weighed


platinum crucible and changed to calcium oxide with

a Bunsen flame, or blast lam p .

7 . To determine the MgO .

Treat the filtrate from 6 as in previous cases .

8. To determ ine

Provide a sm all flask with a rubber stopper andbulb tube . The upper end of the tube should be

closed with a rubber tube and glass p lug. With a

sharp knife cut a slit about a half- inch long in therubber tube . This serves as a valve to let the gas

escape, but allows no air to entersl' Weigh a portion

of the substance into this flask,to which add a sm all

quantity of dilute hydrochloric acid . Dissolve the

powder by gently warming. When efiervescence

ceases,add one or two sm all crystals of sodium car

bonate to create an atmosphere of carbon dioxide .Cool

,and precipitate with an excess of barium car

bonate . Filter as rap idly as possible with the pump,wash thoroughly in cold water

,and discard the fil

trate . Dissolve the p recip itate in warm,dilute hydro

chloric acid,remove the barium with dilute sulp huric

acid,and determine the iron as in 3. Subtract the

percentage of iron here obtained, which is the percentage of ferric oxide sought

,from ' the total per

centage obta ined in 3. Reduce the difference to FeO,

which is the percentage of ferrous oxide sought .

The m ethod of Berzelius as im p roved by Bunsen.

1It is known as the Bunsen valve.


Remarks.

The basic acetate method of precipitating ironand alumina .

This method is applicable when manganese is pres

ent as in dolomite and siderite,and further in Ger

man silver, smaltite, fahlerz, and granite .

The acid filtrate from the silica is diluted quitelargely with water. A solution of ammonium car

bonate is gradually added,and with constant stirring

until the precipitate,which forms at first

,is dissolved

with difficulty . In the case of siderite, the solutionwill now be deep brown in color. The addi tion of

ammonium carbonate is continued until a very slightprecipitate forms

,which alm ost disappears when the

liquid is stirred, the solution remaining slightly

opalescent. A little acetic acid and a moderatequantity of a strong solution of ammonium acetate

are added,and boiled for some time . It is filtered

while hot, and the p recipitate is washed with boilingwater. The filtrate and washings m ust be clear andcolorless .

To separate the manganese, which m ay have beenprecipitated with the iron and alum ina, the p recip i

tate is dissolved in warm hydrochloric acid andtreated as before— with ammonium carbonate, aceticacid

,and ammonium acetate . The precipitate con

sists of the iron and alumina as basic acetates,and

they can be separated and determined in the usual

way.


tinguish the burners and allow the apparatus to

cool.

Place the tube on the black glazed paper, and witha file break it into small pieces . Remove these to anevaporating dish

,cover with water, and warm thirty

minutes . Then with a pair of clean crucible tongs

take up each piece of glass and wash the contentsinto the evaporating dish with hot water . Filter withthe pump . The filtrate contains sulphates and so

dium carbonate . Add hydrochloric acid until bub

bles of carbon dioxide no longer escape . Heat to

boiling to remove all the gas . Precip itate the sul

phate with barium chloride . Let stand a day before

filtering. From the weight of barium sulphate, the

percentage of sulp hur can be computed .

2. S ilica and lead .

Place a gram of the substance in an oxidationcrucible of 150“ capacity, and holding a watch-glassin one hand pour on 40“ of fum ing nitric acid .

Q uickly cover the dish with the watch-glass and letstand over night. Still covered, heat the substancecarefully on the water-bath until the brown fumes ofnitrogen peroxide have all disappeared . Rinse thematerial on the glass into the dish and evaporate to

dryness . When dry add about a teaspoonful of dilute

sulphuric acid and evaporate until there is no m ore

odor of nitric acid . Subsequent additions of sulp hu

ric acid may be necessary to accomplish the result.Transfer the substance to a small beaker and boil .

Let stand a few hours and filter 0 3 the precipitate,


which consists of silica and lead sulphate . Wash

eight or ten times with water containing ten or twelvedrops of dilute sulphuric acid in 100“ of water

,to

prevent the solution of the lead. Remove the sul

p huric acid from the filter by washing it four or five

times in 95 per cent alcohol . Collect the alcoholicfiltrate in a separate beaker

,and if it is not perfectly

clear pass it through the filter again . I f clear, throwaway.

Dry, heat, and weigh the precipitate . Treat in the

crucible with warm nitric acid,which dissolves the

lead but does not afi ect the silica. Decant the solution in a small beaker

,and repeat the nitric acid

treatm ent a number of times . Then transfer all fromthe crucible to the beaker and heat to boiling. Let

stand two or three hours and filter the silica, the

amount of which is determined in the usual way .

Deduct this amount from the weight of both to find

the percentage of lead .

3 . Copper.

Dilute the filtrate from 2 largely with water,*

place it in a beaker which is covered with a perforated watch-glass . Through the watch-glass, passa stream of sulphuretted hydrogen for about an hour .Filter with the pump, and wash with water to whichsuflicient sulphuretted hydrogen has been added torender the odor perceptible ?

CuS is soluble in sulp huric acid unless very dilute.

1CuS very easily oxidizes in the air to CuSO4. The sul

phuretted hydrogen p revents Oxidation.


Dry the precipitate and remove with the filter

ashes to a Rose crucible . Prepare a hydrogen ap

paratus, from which the gas is dried by sulphuric acidand calcium chloride. (Fig. Heat the crucibleto redness without the cover. Add a little sulphur

on the point of a knife, turn the stream of dry hydro

gen into the crucible through a cover having a hole in

the centre . Place a small flam e under the crucibleand continue heating until there is no more odor of

sulphur dioxide . Add another sm all portion of sul

phur, and treat with the hydrogen as before, havingthe flam e underneath. When no further odor of

sulphur dioxide is perceptible,extinguish the burning

hydrogen, rem ove the flam e,and allow the stream of

hydrogen to continue until the tem perature of the

crucible is about Remove to the desiccator andweigh as usual . Repeat with the sulp hur and hydrogen to constant weight. This treatm ent gives Cu,S,from which the amount of copper is determined .

4. Iron .

Concentrate the filtrate from 3 in a flask, whichalso removes the sulphuretted hydrogen . Transfer to

a beaker,oxidiz e the iron with fum ing nitric acid,

add about two grams of ammonium chloride, and precip itate with amm onia . Determine as in previous

cases .5. CaO .

Concentrate the filtrate from 4 and proceed asusual.


Concentrate the filtrate from 5 and proceed as

before .

7 . C0 2 .

The Bunsen method can be used ; but in a sulphidelike chalcopyrite and sm altite it is necessary to p re

vent the escape of hydrogen sulphide, as this wouldgive too high a result in CO, . This is accomp lished

by the use of dilute sulphuric acid instead of hydro

chloric acid . I f there is still an odor of hydrogen

sulphide,or if lead paper should indicate the forma

tion of the gas,a small quantity of powdered copper

sulphate,ferrous sulphate, or potassium dichromate

is introduced into the bulb with the p owdered m ineralor rock, and the determination can proceed as inother cases .

" . Sodium Phosphate. Na2HPO 12H

20 .

l . The acid, P20 5 .

Weigh a gram of the substance in a sm all beakerand dissolve it in a little water . In another beakerplace a small quantity of magnesium chloride, whichshould be dissolved in hydrochloric acid . Then add

ammonia to alkalinity . If a precip itate forms, it

m ust be dissolved by a little more hydrochloric acid .

Let this m agnesia m ix ture cool, and with it p recip itate the solution of sodium phosphate . Add to the

whole one-third its bulk of amm onia water and letstand some hours before filtering. When heated to

redness the substance becomes magnesium pyrophos


phate,from which the percentage of P

20, can be

com puted .

2. The base, Na20 .

Evap orate the filtrate from1to dryness in a platinum dish and drive off the am m onium chloride withthe free flame as in determin ing the base of potassium

bichromate . Then add about 200“ of baryta water,again place the dish on the water-bath, and evaporateto dryness . Dissolve the residue in a little water andfilter with the p um p . The filtrate soon absorbs car

bon dioxide from the air, and the barium carbonatethus form ed causes a turbidity of the liquid, whichis easily removed by a few drops of hydrochloricacid .

Precip itate the barium with the smallest possibleexcess of dilute sulphuric acid . Filter. Evap orate

the filtrate in a platinum dish until there is no further

decrease in volum e . Then with the direct flame con

tinne the heating to rem ove the excess of sulphuricacid . The residue still contains barium sulphate . To

rem ove this,dissolve in a little water and filter in a

weighed platinum crucible . Evap orate the filtrate

to dryness on the water-bath and heat further withthe free flam e to exp el all moisture . The substance is

now acid sodium sulp hate, and it m ust be changed tothe neutral salt. To accom p lish this, add, two or

three times,a piece of am m on ium carbonate as large

as a pea, and heat the crucible to redness after each

addition . Repeat to constant weight.3. Water .


Place a gram of the substance in a weighed p orcelain crucible and heat in an air-bath at 300 °

to constant weight.


"I. German Silver.

Composition : Copper,zinc, and nickel, together

with sm all quantities of tin , lead, and iron as impurities .

Clean about a gram of the alloy by the use of seasand and water.

1. To determine the tin .

Dissolve the substance in a small beaker by gentlyheating, covered, with 50“ of dilute nitric acid . A

small precipitate of tin hydrate may appear,and

should be treated as in the analysis. of the silver coin .

2. To determine the lead .

*

Evaporate the filtrate from1in a porcelain dish todryness on the water-bath. Add 10“ of dilute sulphuric acid and continue the evaporation until there

is no odor of nitric acid . It may be necessary to add

If a qualitative analysis does not disclose the p resenceof lead, determ ine the cop per at this stage.


appears as a coloration on the filter p ap er . It be

comes Pezo,on heating to redness in the crucible .

5 . To determ ine the z inc .

Evap orate the filtrate from 4 to a convenient vol

um e, and while still on the water-bath add a solutionof sodium carbonate . Th is p recip itates both z inc

and nickel as carbonates . Let rem ain a half-hour on

the water—bath to exp el the carbon dioxide . Filter

with the pum p and wash with hot water .With a feather and the free use of water, transfer

the p recipitate to a porcelain evap orating dish, savingthe filter on account of the sm all quantity of p recip

itate that rem ains up on it . Place the substance upon

the water—bath, concentrate to a sm aller bulk if necessary

,and add sm all am ounts of hydrocyanic acid and

caustic potash solution until the green carbonatesgive place to a substance

,of uniform whiteness . The

two reagents em p loyed form p otassium cyanide .

While adding them,a watch-glass must cover the

dish,as there is an evolution of carbon dioxide . Con

tinue to heat on the water-bath until all carbon dioxide has p assed away. To secure the white appearance it m ay be necessary to add two or three portionsof the hydrocyanic acid and caustic potash . Finally,evaporate the solution to a sm all bulk .

The precipitate is nickel p aracyan ide, which hasbeen form ed in the op eration . Filter through the

pap er that contained the nickel and zinc carbonates

and dry the p recipitate .

The warm filtrate in a porcelain dish on the water


bath should be precipitated with potassium sulphide .

*

Filter and wash the precip itate with water containinga little of the reagent, to prevent the oxidation of the

zinc sulphide .

Dissolve the precipitate on the filter with warm

dilute hydrochloric acid . Evaporate the zinc chlorideto a convenient size, and then filter into an evap orat

ing dish to remove the sulp hur . Place the dish on

the water-bath, and covering with a watch-glass, precip itate the zinc with a small excess of sodium carbonate. Let the substance stand a few minutes onthe water-bath and filter with the pum p . The z inc

carbonate when heated to constant weight becomesz inc oxide .

6. To determ ine the nickel .

Evaporate the filtrate from 5 to dryness, and hav

ing the dish covered with a watch-glass add hydrochloric acid, stirring with a glass rod . Evaporate

again to dryness and then add aqua regiasl' This de

stroys the organic matter,and the green color should

appear at least after two or three additions of the

reagent. The yellow coloration is due to nickel paracyanide . Evaporate to dryness and add to the resi

due about 50“ water. Filter, wash, and dry the precip itate.

There are now two filters containing nickel para

This is m ade by taking equal weights or volum es of a

solution of caustic potash , saturating one p ortion with

hydrogen sulph ide, and pouring into th is the other portion.

1-3 p arts Hcl and 1part HNOs.


cyanide . Ignite them in a porcelain crucible and dissolve t he nickel in a little dilute hydrochloric acid.

Remove the silica which the alkalis have dissolvedfrom the porcelain, and the ashes, by filtering. Add

this filtrate to the main portion of the nickel, —the

filtrate from the second portion of nickel p aracyan ide,— and precip itate as hydrate

“with a concentrated so

lution of caustic potash . When heated to redness

this becomes nickel oxide N iO .


Total 100 . l l

" II. Smaltite.

Com p osi tion : Cobalt arsenide or cobalt-nickelarsenide, together with sulphur, silica, z inc

,iron

,

copp er, bism uth, lead, calcium ,m agnesium

,and car

bon dioxide .

The p recip itate of nickel hydroxide should be washedfifty or six ty tim es with boiling water, until th e wash ingsgive no cloudiness with a solution of Silver nitrate. Afterthe p recip itate is ign ited, it m ay be necessary to wash the

nickel ox ide again with boi ling water.


A. 1. To determ ine the 0 0 2.

Proceed as in previous cases .2. To determine the sulphur .

Place a gram of the p owdered mineral in an oxidation crucible and add 50“ of dilute nitric acid . Cover

with a watch-glass and heat on the water-bath untilthe evolution of gas ceases . Rinse the contents of thewatch-glass into the crucible and evaporate to dryness .

Then add successive portions of dilute hydrochloric

acid, evaporating each time to dryness until no more

odor of nitric acid can be observed . Transfer the

substance to a small beaker, boil upon the addition ofwater, and after standing some hours filter .

The precip itate contains silica and lead sulphate .

Place the paper in a small beaker,add dilute hydro

chloric acid, and boil to dissolve the lead sulp hate .

Filter into the preceding filtrate . Dilute the filtrates

with water,heat to boiling, and precipitate with

barium chloride . Let stand a day and filter. Fromthe amount of the barium sulphate compute the per

centage of sulp hur.B . To determ ine the bases and silica .

1. Lead and silica .

Place a gram of the substance in an oxidation cru

cible and add nitric acid, as in the determination ofsulphur . Rem ove the nitric acid with sulphuric acid.

Transfer to a small beaker and heat to boiling. Filter.

The precipitate contains silica and lead sulphate,

which are treated as in chalcopyrite .2. To determine the arsenic .


Dilute the filtrate from 1to a volume of 200“ and

heat to 60° This tem p erature m ust be main

tained from three to si x hours, while a stream of sul

p huretted hydrogen is run through the liquid . The

loss by evaporation m ust be supplied . This p recip i

tates arsenic,bismuth, and copper, while the other

substances remain in solution . Filter with the pum pand wash well with cold water . Remove the p recip itate to the sam e beaker and warm with potassium sul

p h ide. This dissolves sulphides of arsenic, but does

not change the copper and bismuth sulphides . Now

filter through the p aper from which the p recipitatewas rem oved . Wash in cold water

,dry, and keep for

future work upon it.Evap orate the original filtrate from the sulphides

to a smaller volume, heat to 60° and again pass

through the liquid a stream of sulphuretted hydrogen .

In case the arsenic, bism uth, and copper were not allprecipitated the first tim e, more will be thrown down .

This must be treated with potassium sulphide as be

fore . Filter off the cop per and bism uth and dry.

Evap orate the solutions of arsenic to dryness on

the water-bath . If sulphides of bismuth and copper

separate from the solution, as is quite likely, filter,and keep the precipitate with the other two p ortions .Transfer the arsenical residue to an oxidation cru

cible, using as sm all a quantity of water as possible .

Add about seven grams of solid caustic potash, wh ichthe water should dissolve . Then for about twentym inutes pass a stream of Chlorine free from air into


the crucible, which is kept warm on the water-bath .

The gas has run sufficiently long when the substancebleaches litm us pap er . It is necessary to have a

wash bottle at hand, as the potassium chlorate whichform s may clog the delivery tube .

With the crucible covered by a watch-glass,add

about 50“ of dilute hydrochloric acid to decompose

the p otassium chlorate which has form ed . Evap orate

on the water-bath until crystals appear . Then rep eatthe operation

,using 50“ of concentrated hydrochloric

acid .

By the use of hot water, transfer the contents ofthe crucible to a beaker glass and filter to rem ove

the sulp hur and silica. If,upon the paper

,yellow

flakes of arsenic sulph ide appear, they must again be

transferred to the oxidation crucible , and the treat

ment with caustic potash,chlorine

,and hydrochloric

acid repeated . Finally filter off the silica and sul

phur . The two filtrates containing arsenic are now

united and kep t three to six hours at 60°

— 70°

while a

stream of sulphuretted hydrogen is run through . The

precipitate is As,S, .

The sulphides of arsenic cannot be strongly heated

on account of their volatility . They are determ ined

as follows : A filter paper on a watch-glass i s heated

for three hours in a therm ostat at 105 ° It is

transferred to a weighing bottle, and its weight determined. Return it to the therm ostat for half an hourand again weigh

,repeating if n ecessary until constant

weight is attained.


The arsenic is filtered through this paper, washedwith cold water

,and then wi th alcohol three or four

times to convert the amorphous into crystalline sul‘

phur, which is soluble in carbon disulphide ; then fouror five times with carbon disulphide, and again withalcohol . Place in the thermostat and heat (cautiously

at first,lest the alcohol take fire) to 105

°

—110 ° to

constant weight. The substance and p aper are

weighed each time in the weighing bottle . From the

amount of sulphide,the percentage of arsenic can be

comp uted.

3 . To determine the iron.

The filtrate from the sulphides of arsenic, bismuth,and copper is placed in a beaker, covered with awatch-glass, and heated to remove the hydrogen sul

p hide. It is oxidized with fum ing nitric acid. Heat

the solution to boiling and neutral ize with crystals ofsodium carbonate . Precipitate the cool solution withsodium succinate.

4. To determine the nickel. Liebig’

s method.

The filtrate from 3 is evaporated in a porcelaindish to a small volume. If more iron separates out,filter. If the solution rem ains clear

,add a solution

of caustic potash to the substance on the water-bath,which precip itates the nickel and cobalt as hydrates,N i (OH) 2 and

Let remain about twenty m inutes on the water

bath, until the hydrates become a dirty bluish-green

color. Filter with the pump and wash with hot

Water . The p recipitate is removed from the p aper


little hot water and filter 0 3 the mercury salt that itmay contain . Wash the precipitate well with hotwater and evaporate again to dryness ; add a

little hot water and again filter, to remove the

last trace of mercury, into a porcelain evaporatingdish.

Place the filtrate on the water-bath and precipitatewhile hot with a solution of caustic potash . The sub

stance is a dark color when sufficient of the reagenthas been added. Filter the precipitate, wash thor

oughly in hot water, dry as usual, and remove to a

weighed porcelain crucible. Add a centim etre ofwater, and test the liquid with strips of red and bluelitmus paper. I f the reaction is alkaline, the p recip itate must be further washed to remove the causticpotash. If it reacts acid, this is due to which

has an acid reaction, and more caustic potash m ust beadded to the solution to precipitate all the cobalt. Ifthe reaction is neutral, evaporate to dryness on thewater-bath, and heating with a small flame reduce

to m etallic cobalt with a stream of dry hydrogengas .

6. To determine the z inc.Heat the filtrate from 4 to boiling, add a little

acetic acid, and for half an hour run a stream of sul

p huretted hydrogen through the liquid . Filter and

wash the precipitate with water containing a littleacetic acid. Treat the dry z inc sulphide in a Rosecrucible with hydrogen and sulphur, as in the deter

m ination of copper in chalcopyrite.


7. To determine the calcium .

Evaporate the filtrate from 6 to a smaller volume,

filter off the sulphur, and proceed as before .8. To determ ine the magnesium.

Proceed as before.9. To determine the bismuth .

Transfer the p recipitates of bism uth and copper toa crucible and heat. This changes the sulp hides to

oxides . Dissolve the oxides in warm nitric acid andfilter . Wash the paper with hot water which contains a little nitric acid to prevent the precipitationof bismuthyl nitrate Add ammonia to

the filtrate on the water-bath,which precipitates the

bismuth as hydrate

10. To determine the copper.

Precipitate the filtrate from 9 with sulphuretted

hydrogen and determine as in previous cases

" III . Fahlerz.

Composition : Copp er, arsenic, and antim ony sul

p hides. It m ay also contain water, m ercury, silver,iron

,silica

,zinc, cobalt, nickel, manganese, lead, cal

cium and magnesium carbonates .Ten grams should be pulverized, as five portions

are necessary : one for the sulphur determination, one

for carbon dioxide, one for water,one for mercury,

and one for the other bases .

A. 1. To determine the C0 2 .

Proceed as in previous cases .


2. To determine the sulp hur .

Use the combustion furnace as in chalcopyrite .B . To determine the bases and silica .

l . Antimony.

Place a portion of the substance in a platinum

crucible,nearly fill the crucible with freshly prep ared

potassium sulphide,and let it remain fifteen minutes

on the water—bath,stirring occasionally with a plati

num sp atula . Decant the clear liquid into a two- litre

beaker and repeat the treatm ent with potassium sul

ph ide s ix or seven times . Then pour the contents ofthe crucible into the beaker, washing the crucible aswell as p ossible . Some of the sulphides will cling tothe walls, but no attention is p aid to this until later,when it i s dissolved in nitric acid and added to therem ainder of the sulphides treated with the sam e

reagent .

Add a litre and a half of water to the beaker,stir thoroughly with a glass rod for ten minutes,and let stand over night. The arsenic and anti

mony are in solution, while the remaining sulph idesare undissolved . Filter with the pump and washwith cold water. (Hot water usually causes sul

ph ides to oxidize .) Dry the precipitate and re

move with the filter ashes to the oxidation crucible.Dissolve the sulphides rem aining on the platinum

crucible with fuming nitric acid,place this also in the

oxidation crucible with m ore nitric acid to ox idize the

sulphides to sulphates . Let stand three or four hours

and evaporate to dryness . Add a little water and


ex actly neutralize with a solution of caustic potash.

Exact neutralization at this stage is highly important"“

Then add 50“ p otassium sulp hide in successive por

tions to extract the rem ainder of the arsenic and

antimony. Decant into a large beaker,adding finally

the undissolved residue . Dilute largely with water,

let stand over night,and filter in the morning.

The filtrates from both extractions are united and

strongly acidified with sulp huric acid . This p recip i

tates the arsenic and antim ony .

After standing twenty- four hours,

filter with a

p ump, and with a feather transfer the precipitate toa porcelain evaporating dish. Add a dilute solution

of caustic p otash and leave on the water—bath untilall is dissolved . Concentrate the solution, and filterif there is a separation of cop per sulphide . Collect

the filtrate in an oxidation crucible and evap orateuntil there is a layer on the bottom about a centimetre

deep .

Add to the crucible about ten grams of solid caustic

p otash with sufficient water to dissolve it. Then passthrough a stream of chlorine

,until the substance only

bleaches litm us, to oxidize fully the arsenic and anti

m ony . Decom p ose the p otassium chlorate with dilute

and concentrated hydrochloric acid,as in smaltite .

Remove the substance from the crucible into a large

If free acid is p resent, the p otassium sulph ide is decom

p os‘ed, and the arsen ic and antim ony would not be dissolved.

If there is an ex cess of the alkali , som e iron m ight go into

solution, which would not be estim ated.


beaker,add 200“ of strong hydrochloric acid, and

then suflicient dilute hydrochloric to dissolve the p otassium chloride . Filter off the silica which was dissolved from the crucible, and to the filtrate add 200“

sulphuretted hydrogen water,which precipitates only

the antimony . Filter, and by an aspirator or filterpump conduct air through the filtrate for a number ofhours to remove the sup huretted hydrogen .

Dissolve the antimony on the filter with potassium

sulphide into a cleaned, dried, and weighed platinumdish of 100“ capacity . Concentrate the solution until

the dish is half full . Place the dish on the negative

pole of a Bunsen cell and introduce into the liquid acoil of platinum wire, suspended from the positive

pole. Let the electric current pass through eight totwelve hours . To ascertain when all is decomposed,by means of a capillary tube withdraw two or threedrops, place in a sm all watch-glass, and add a drop ortwo of sulphuric acid . If only a whitish precipitateresults

,it is sulphur, and the decomposition is com

p lete. Without disturbing the deposit of antimony,

p our the liquid from the dish, wash four or five timeswith water and then with alcohol . D ry in the desic

cator and weigh .

2. To determine the arsenic .

The filtrate through which the stream of air haspassed is placed in a beaker and precipitated at a

tem perature of 60°— 70

°

with a stream of sulphurettedhydrogen . It is filtered on a weighed paper and determ ined as in smaltite .


3. To determine the lead and silica.

The sulphides from which the arsenic and antimonywere removed are placed together with the ashes ofthe filter in an oxidation crucible and treated withfuming nitric acid. Evaporate to dryness and expel

the nitric with sulphuric acid . Add 200“ water, heatto boiling, and filter . The precipitate consists oflead, silica, and a little iron .

Dry the precipitate, remove it with the filter ash toa weighed porcelain crucible, heat to redness, andweigh . Treat it with 15“ nitric acid and heat to boiling. Filter, and determine the silica as usual .Oxidi ze the filtrate with fuming nitric acid and pre

cip itate the iron with ammonia . Determine the weight

of the iron . The amounts of iron and silica now beingknown, the percentage of lead can be computed.

4. To determine the silver.

To the filtrate from 3 add two or three drop s dilutehydrochloric acid . A larger quantity of acid might

dissolve the silver chloride which is contained . The

small quantity of chloride usually present is reducedto metallic silver by the burning paper.5 . To determine the copper .Treat the filtrate from 4 with sulphuretted hydro

gen . Filter, and wash the precipitate with dilutehydrochloric acid

,and then with water containing sul

p huretted hydrogen, as in German silver . Add thisportion to that which separated out in connectionwith the antimony determination, and estimate as in

previous cases .


6 . To determine the main portion of the iron .

Evaporate the filtrate from 5 to a smaller volum e

to expel the sulp huretted hydrogen . Oxidize withfum ing nitric acid, neutralize wh ile hot with sodiumcarbonate, and p recipitate the cold solution with so

d ium succinate . The iron thus obtained i s to be

added to that received in connection with the determination of lead and silica .

7. To determ ine the z inc,nickel

,and cobalt .*

Acidify the filtrate from 6 with acetic acid . Heat

on the water-bath to boiling to see if m ore iron willseparate out. If not, introduce a stream of sulp huretted hydrogen for half an hour . Wash the p recip i

tate in water containing am m onium acetate . Treat

like z inc sulp hide in sm altite .

8. To determ ine m anganese, calcium, and mag

nesium .

These are usually present in sm all quantities, i f at

all, and can be estim ated together . Evaporate the

filtrate from 7 to a volum e of 40“ and if sul

phur ap p ears, filter . Precip itate on the water-bathwith sodium carbonate. Dry the precip itate, and

determ ine as usual in a porcelain crucible .

9. To determ ine the m ercury .

The m ethod is Sim ilar to that em ployed in the esti

m ation of sulp hur in chalcopyrite . The tube should

be about 60cm in length . At the bottom , there should

be a layer, 5cm in depth , of m anganese carbonate

The nickel and cobalt are usually p resent in such sm all

quantities that they can be estim ated with the zinc.


the bulb tube, the first having been weighed . Connectan aspirator to the second calcium chloride tube. The

third calcium chloride tube connected with a washbottle containing sulphuric acid is attached to theother end of the bulb tube . While heating the bulb

with a Bunsen flame, draw air through the apparatus .

The moisture will collect in the weighed tube, and thepercentage can be computed.

"IV. Phosphorite (Apatite) .

Composition : Mainly calcium phosphate. It also

contains magnesia, alumina, silica, iron, chlorine, fluorine, carbon dioxide, and water .A. 1. To determine the C0 2

.

Proceed as in previous cases .2. To determ ine the fluorine .

Place two grams of dry sodium carbonate in a platinum crucible, then a gram of the powdered m ineral,and three grams of sodium carbonate. Mix well witha platinum wire arranged in the form of a corkscrew.

Cover the crucible and heat for ten minutes with a

Bunsen flame, and then for half an hour with a blastlamp, until all is fused and no more carbon dioxideescapes .* Cool by blowing air with the bellowsagainst the sides of the crucible .

The crucible containing the substance in a state of

fusion m ay be grasped with the tongs and given a rotarym otion . This distributes the substance upon the Sides of the

crucible, by wh ich i t m ay m ore easily be rem oved.


Transfer the crucible and its contents to an evapo

rating dish, cover with water, and heat for half an

hour on the water-bath. Filter, and wash with hot

water . Fusing with sodium carbonate changes calcium chloride and fluoride to the sodium salts which

are in the filtrate .

Place the filtrate in an evaporating dish on the

water-bath, and add 15“ of a solution of ammoniumcarbonate to precipitate the silica . Filter, and washwith hot water .Again transfer the filtrate to the water-bath and

add a little ammonium zinc sulp hate .

* Evaporate

to dryness on the water-bath,stirring with a glass

rod to a fine powder. Add hot water and filter with

the pum p .

Acidi fy the filtrate with acetic acid,and to it add

a solution of calcium chloride as long as a precipitatecontinues to form

,and then a few drops of a solution

of sodium carbonate . Heat on the water-bath untilcrystals appear. Filter, wash, and dry the p recip i

tate. Heat it with the filter ash in a porcelain crucible . Transfer the contents of the crucible to a

sm all evaporating dish and again treat with aceticacid . Filter, dry, and heat the precip itate, wh ich i scalcium fluoride, to dull redness . From the am ount

obtained, the percentage of fluorine can be deter

mined.

Th is is m ade by dissolving zinc in sulphuric acid, fi ltering, and adding to the filtrate sufficient am m onia to dissolvethe p recip itate which form s at first.


3. To determ ine the chlorine .

A gram of the substance is fused with sodium car

bonate and treated with water, as in the case of fluorine . Acidify the filtrate with nitric acid and add asolution of silver nitrate to precipitate the chlorineas silver chloride . Let stand som e hours in a dark

place and filter. In burning the paper,the chloride

is changed to metallic silver,from the weight of

which the chlorine is easily determined .

B. To determine the bases,phosphoric acid and

silica .

1. Silica .

Place a gram of the substance in a porcelain evap

orating dish and add nitric acid, covering with awatch-glass during the evolution of gas . Remove thecover and evaporate to dryness .

When about the consistency of syrup, stir the substance with a glass rod, during the further evapora

tion, until a fine dry powder results . Then add 50“

nitric acid and about the sam e quantity of hot water,and leave for fifteen m inutes on the water-bath . F il

ter . The precip itate contains silica and a small quantity of iron . Dry. Heat the precipitate to redness

in a porcelain crucible, cool, and weigh .

Treat the precipitate on the water-bath with dilutehydrochloric acid . Let it remain a few moments onthe water-bath and decant the clear liquid into a

beaker . Rep eat this several times until the iron isdissolved . Transfer the residue to the beaker whichcontains the liquid

,heat to boiling, let stand some


hours, and filter . Transfer the dried precipitate andfilter ash to a weighed porcelain crucible and determ ine the percentage of silica . Precipitate the ironin the filtrate with ammonia and determ ine the per

centage . This is to be added to another portion determ ined later.

2. To determine the phosphoric acid, as P20 5.

Evaporate the filtrate from 1almost to dryness,add about 30“ nitric acid, and while covered, addtwo gram s of tin foil in sm all pieces . The tin uniteswith the phosphoric acid, form ing the phosphate

When nitrogen peroxide ceases to come off, removethe watch-glass and filter with the pump . By the use

of water, remove the precipitate to a porcelain evapo

rating dish and warm on the water-bath . Then add

sufficient solution of caustic potash to dissolve it.Filter through the paper from which the tin wasrem oved

,and wash with hot water ( save the paper

for subsequent treatment, as it may contain iron) .

Dilute the filtrate with water to one and a halflitres

,acidify with sulp huric acid, and run a

stream of sulphuretted hydrogen into it for three

hours .Let stand over night and filter . Wash si x times

with undiluted sulphuretted hydrogen water .Transfer the filtrate to a large flask and concen

trate to a bulk of loo“ Again pass through

the liquid a stream of sulphuretted hydrogen to pre

cip itate any tin that m ay have oxidized and gone intosolution.


Filter and wash with sulphuretted hydrogenwater

as before . Evaporate the filtrate to expel sulp hu

retted hydrogen, oxidize with a few drop s of fuming

nitric acid, and add ammonia to precipitate the iron,which frequently comes down with tin and is in solution as iron sulphate . The ammonia precipitates the

iron as phosphate (FePO,) from the amount ofwhich the Fezo, and P20 , can be computed . Both

are to be added to portions that will be separated

later.

The filtrate from the iron phosphate i s precipitatedwith magnesium ammonium chloride, magnes ia mixture

,prepared as in the analysis of disodium phos

phate. The magnesium ammonium phosphate thus

formed is treated in the customary way .

3. To determine alum ina and the remainder of theiron.

Treat the filtrate from 2 with a current of sul

p huretted hydrogen to remove traces of copper, zinc,and lead which are present in tin foil and may still be

in solution . Filter with the pump and wash with coldwater. Heat the filtrate to boiling to expel the sul

phuretted hydrogen . Oxidiz e with fuming nitric acidand add ammonia to slight alkalinity. Heat again to

expel the excess of ammonia . Filter with the pump

and wash with hot water. Dry, heat, and weigh theprecipitate .Nearly fill the crucible with dilute hydrochloric

acid, let it stand ten minutes on the water-bath, anddecant the clear liquid . Repeat until all is dissolved.


Filter to remove the ashes, and collect the solution in

a small platinum evaporating dish .

Place the dish on the water-bath, and evaporate toa small bulk to remove the greater portion of the

hydrochloric acid . Add a solution of caustic potashto p recipita te the iron, while the aluminum-potassium

compound that forms is soluble .Filter the iron with the pump

,wash well with hot

water, and discard the precipitate .

*

To the filtrate add hydrochloric acid to slightacidity, and precipita te the alum ina with freshly prepared ammonium sulphide . Wash with hot water .

The heated precipitate is AlzO,

. This subtractedfrom the weight of iron and alumina obtained in theforegoing gives the rem ainder of the iron .

4. To determine the calcium ox ide .

The filtrate from 3 is treated with ammonium ox

alate and determined as usual .

5. To determine the magnesium oxide.

Concentrate the filtrate from 4 to smaller bulk andproceed as before .

To determine the water.

Proceed as in fahlerz . The use of lead oxide isnot necessary here .

Iron in a solution containing caustic p otash cannot bethoroughly washed, and hence in the p resent case the alum ina

must be determ ined. Another m ethod of sep arating ironand alum ina is given in connection with the analysis of

dolom ite.


"V. Granite.

The constituents vary, but the analysis of a type

is here described. It was found to contain silica,molybdenum sulp hide, calcium, m agnesium, alum ina,potassium , sodium, ferrous and ferric iron, titanic andphosphoric acids

,and water.

Fifteen grams should be finely pulverized, andbolted through a fine cloth . The bolting is necessary,as otherwise coarser particles of silica m ight not be

acted upon by sodium carbonate when fused withthat substance .

A. To determine the acids .1. C0 2 . Determined in the usual way .

2. To determ ine the Bettel’

s method .

Place a gram of the substance in a porcelain crucible and add two grams of acid potassium sulphate .Mix with a platinum wire and m oisten with a fewdrops of sulphuric acid . Place high over a sm all

flame and heat three hours with the crucible closed .

The flame should be so regulated as to send off a

steady stream of sulphur trioxide.Cool the crucible, and place the substance in a

beaker of water, and let it stand over night to dis

solve . The double salt, potassium -titanium sulphate,which has formed, is soluble in water . Filter. Washwith cold water and set the filtrate aside .

Tio2

IE IISO4

K2Ti (SO K

ZSO

4

Boiling : s uso 2KHSO,+

11280

4.


which m ay have been precipitated with the phos

phate .

Dissolve the contents of the filter by pouring warm

amm onia upon it. Precip itate the solution with magnesium ammonium chloride and determine as inprevious cases .The filtrate from the ammonium phosphomolybdate

often contains more phosphoric acid ; and heating

and allowing it to stand with an excess of the am

m onium molybdate will often give a second p recip i

tate. This should receive the same treatment as the

first portion.

4. To determine the silica .

Place in a platinum crucible two grams of sodiumcarbonate, a gram of the substance, and five gramsof sodium carbonate . Mix all thoroughly with a

platinum corkscrew. Heat for fifteen minutes with

the crucible covered,over a Bunsen flame

, to allowsome of the carbon dioxide to escape. Then transferto a blast lamp and heat, covered, to complete fusion,or until no more gas escapes . Blow air against the

walls of the crucible,more easily to remove the con

tentsf Remove the fused mass to a beaker, add waterto the Crucible, and heat to boiling. Repeat a numberof tim es. Finally add dilute hydrochloric acid to dissolve all the substance adhering to the crucible .

Treat the contents of the beaker with dilute hydrochloric acid, as long as there is an evolution of gas, todecompose the carbonates . Heat to boiling until all

the carbon diox ide is driven ofi'

.


Transfer the contents of the beaker to a porcelaindish and evaporate to dryness . Commence to stirwith a glass rod as soon as crystals of com m on saltappear, as they tend to enclose other substances whichwould be estimated as silica .

When perfectly dry and fine add sufficient dilutehydrochloric acid to moisten well the powder. Leavefor fifteen minutes on the water-bath to change theox ychlorides into norm al chlorides .

Filter Off the HzS iO, with the pump and wash with

hot water. Dry and place the substance with thefilter folded over it, to enclose it, in a

.

clean weighed

platinum crucible. Press it down with the finger to

make it fit snugly in the corner. Wipe the funnel

with another small filter paper, and place it over the

one enclosing the silica and moisten with a few dropsof water.Place the crucible on a triangle in a slanting posi

tion, and commence heating the outer edge with avery small flame

, gradually increasing it and moving

downwards. When the m oisture is removed,employ

the full flam e until all is white. The substance is very

fine and easily escapes,but the filter papers serve as

covers to prevent loss . Such carefulness is necessaryonly with silicates

,as other minerals contain the silica

in layers and not in combination . When all is white,place the crucible in an upright position and heat tenminutes longer . Then transfer to a blast lamp and

heat closed for ten m inutes,to remove all moisture .

Heat to constant weight.


Place some com m erCIal hydrofluoric acid in a

platinum still,moisten the Silica in the crucible with

dilute sulphuric acid,and distill hydrofluoric acid into

the crucible until it is three- fourths full . P lace the

crucible on the water-bath to remove the volatile SiF,which has form ed . Rem ove the sulphuric acid withthe direct flame . Cool and weigh . Rep eat the disti llation of hydrofluoric acid, etc .

,until constant

weight is gained . The loss in weight represents the

SiO, .

B. To determ ine the bases .

1. Molybdenum .

The residue in the crucible is now treated withdilute hydrochloric acid and heated until all i s dis

solved . Add this to the filtrate from the silica andpass through it when cold a stream of sulp huretted

hydrogen for half an hour . This precipitates MOS,

and PtSz, the latter having been dissolved from the

platinum apparatus . Th is filtrate, C, heat at once to

boiling to expel the sulphuretted hydrogen .

Pour yellow ammonium sulp hide on the well-washedprecipitate . This dissolves the MOS

,and PtS2 as

double salts and leaves PbS and CuS on the filter,which m ay be estimated if in sufficient quantity .

Place the filtrate from the p receding in a porcelain

crucible and evaporate to dryness . When dry, pass acurrent of burning hydrogen into the crucible, whichis heated with a Bunsen flam e . This reduces the

Pure hydrofluoric acid m ay now be purchased of the

usual dealers.


MOS, to MOS2 and the PtS2 to Pt . After removing

the flame introduce the stream of hydrogen until the

crucible is cool . Weigh, and treat the substance withfuming nitric acid

,which volatilizes the molybdenum

and leaves the platinum .

2. To determ ine the alumina .

Heat the filtrate from1to boiling and oxidize withfuming nitric acid . Add a little am m onium chloride

and precipitate with a small excess of ammonia. This

precipitates the iron and aluminum. Filter. Acidu

late the filtrate D and set it aside .

The precipitate is dried and placed with the filter

ashes in a porcelain crucible and heated . It is then

treated with hydrochloric acid on the water-bath untilall is dissolved, save a sm all portion of H,siO , ,

which

passed through the filter in the beginning as H,siO,.

Filter the silica and add the am ount to the first por

tion received .

Evaporate the filtrate from the silica almost to dry

ness to rem ove the excess of acid . Add about three

grams of solid caustic soda, and leave five minutes on

the water-bath, stirring with a platinum spatula.

Th is precip itates all the substances except alumina.Filter, and set aside the precipitate .

Place the filtrate containing the alum ina on the

water-bath for a few m inutes and acidify with hydrochloric acid . Precipitate with freshly p repared am

m on ium sulphide and determ ine as in phosphorite .

3. To determ ine the iron .

The precip itate that was set aside in 2 is dissolved


in warm dilute hydrochloric acid . Am m onia is added

to alkalinity,which precipitates the total am ount of

iron and titanium . After transferring the precipitateand the filter ash to a porcelain crucible, determinethe weight. From the percentage obtained deduct the

p ercentage of titanium previously obtained, to find

the percentage of iron .

4. Manganese.

Granites frequently conta in a small quantity ofmanganese

,but if after fusion with sodium carbonate

the substance is white or nearly so, manganese is

absent,or is p resent in such small quantities that it

cannot be weighed . If present, determine as in

previous cases .5 . To determ ine the calcium .

The filtrate from 3 is added to filtrate D . Evap o

rate to small volume and treat as usual .

6. To determ ine the magnesium .

Proceed as in previous cases .

7 . To determ ine the alkalis .

(a) K20 .

Place a gram of the substance in a platinum cru

cible and m oisten with sulphuric acid. Distill hydro

fluoric acid into the crucible until nearly full . The

hydrofluoric acid form s with silica H,SiF,, which the

sulp huric acid decom poses into S iF, 2HF, both of

which are volatile .

After evaporating almost to dryness, distill more

hydrofluoric acid into the crucible,and again evap o

rate on the water-bath to rem ove the silica . Then


with the crucible closed, heat with the Bunsen flame

to remove all the sulphuric acid.

Place the crucible on the water-bath, nearly fill

with dilute hydrochloric acid, and decant into a largebeaker. Continue until 200“ of the acid has beenused, completely to dissolve the sulphates . Boil the

contents of the beaker fifteen minutes . If a gritty

residue can be felt on the bottom of the beaker witha glass rod, it is silica . Filter, and repeat the treat

ment with sulphuric,hydrofluoric, and hydrochloric

acids .

Precipitate the sulphuric acid of the sulphates withbarium chloride

,and without filtering

,evap orate to

dryness . When dry, add ammonia and acid ammonium carbonate . This p recip itates all the substancesexcep t the potassium and sodium salts . Filter, wash,and rej ect the precipitate .The filtrate containing p otassium and sodium,

as

well as a little calcium and magnesium,is p laced in a

small platinum dish and evap orated to dryness on

the water-bath, and heated with the direct flame to

remove the ammonium salts . When cool add a little

water and filter . The calcium and magnesium saltsare difficult to remove . Add ammonium carbonate tothe filtrate . Evaporate to dryness, heat to dull redness

,treat with water and filter

,as long as a p recip i

tate continues to form on the addition Of the car

bonate . Ten or fifteen different treatments may benecessary. In evaporating the solution containingammonium carbonate

,the dish must be covered with


a watch-glass during the evoluti on of gas, as the car

bonate decomp oses at 5 5°

— 60°

and the escap e of the

gases m ight occasion loss . Up on the addition Of thelast portion of am m onium carbonate, let stand over

night and filter next m orning. Still a sm all quantityof magnesium will be in com bination with the alkaliswhich cannot be sep arated by this method, but must

be removed later .The last filtrate is evap orated to dryness in a

platinum dish and heated, covered, with a direct flame .

Cool and weigh . Add a drop of hydrochloric acid

and heat. Cool and weigh again . Continue to con

stant weight, which indicates the absence Of am monium salts. The hydrochloric acid keeps the m ag

nesium as chloride, which m ight otherwise changeinto oxide . Each heating m ust be sufficient to melt

the alkalis .

Dissolve the residue in a little water, and if it isnot clear, filter . To the clear solution on the water

bath add about twenty drop s of platinic ch loride, andevaporate to dryness,* when the precip itate should beOf a reddish color . If yellowish, all the Na

2PtCl,

is not in solution . Add a few drops of water andtip the dish back and forth until the m ass flowsquietly . Na2PtCl, crystallizes with two m olecules ofwater

,but it dissolves on adding a few m ore drops of

water,and the mass is movable . Too m uch water

would dissolve som e K,PtCl, .

D O not allow the water-bath to boil, but evaporate, usingas little heat as p ossible.


Nat Cl, to NaCl, HCl, and Pt. The hydrogen must

go through for several hours until the solution is

colorless .When the reduction is complete, filter into a

weighed platinum crucible and evaporate to dryness .Heat to redness, cool, and weigh . After adding a

drop of hydrochloric acid, heat and weigh again .

Repeat to constant weight. This gives the quanti tyof sodium chloride, together with a small amount of

m agnesium chloride .

Dissolve the substance in water and precipitate themagnesium with disodium phosphate and ammonia .

From the amount of pyrophosphate obtained, computethe percentage of magnesium chloride . The data are

thus at hand for determining the percentage of NazO .

8. To determ ine the ferrous oxide (FeO) TheMitscherlich m ethod .

A gram of the substance is placed in a dry,clean

tube Of hard glass about 40cm long. Through a long

funnel tube,introduce 10“ of a solution of sodium

carbonate . Add a drop Of sulphuric acid, and whenthe action ceases, add another drop, and continueuntil 20“ have been added . The carbon dioxidewhich is liberated displaces the air and preventsoxidation .

Melt the tube in the blast lamp to close it. Shakewell, and heat for three hours in the Carius furnace

This determ ination can well be postponed until the stu

dent has had p ractice in titrating with p otassium perm an

ganate.


at 260°- 2ao

°

. Cool the tube and open it with a filescratch and small gas flame . Wash the contents intoa beaker, dilute with water to a volume of half a litre,and titrate with a standard solution of potassium

permanganate .

9. To determine the water .

Proceed as in phosphorite.

To prepare the chemically pure platinic chloridefor alkali separations .

Clean six grams of platinum on the water-bathwith dilute hydrochloric acid . Then add aqua regia

and continue the additions until all the platinum is

dissolved. Evaporate nearly to dryness, add a little

water, and continue the evaporation, adding ten or

fifteen successive portions of water until no furtherodor of nitrogen peroxide is app arent.

Filter the residue,heat the filtrate to boiling, add

caustic soda to strong alkalinity,and a few drops of

alcohol . Acidify with hydrochloric acid and add a

solution of potassium chloride . Let stand over night

and filter in the morning. Wash the precipitate witha dilute solution of potassium chloride .

Thoroughly dry the precipitate,transfer it to an

evaporating dish, and crush to a fine powder. Re

move it to a com bustion tube about 40cm in length .

Place it in the combustion furnace and heat for halfan hour with small flam es while a stream of hydrogen

passes through to reduce it to m etallic platinum .

When cool transfer to an evaporating dish and


wash several hundred tim es (1000—1200) with hotwater

, Iintil a few drops of the washings give no pre

cip itate with silver nitrate . When thoroughly washed

transfer to an evaporating dish and dissolve in aqua

regia . Continue evaporating and adding water untilno odor of nitrogen peroxide is perceived. Dissolve

the residue in water, making a dilute solution.

Remarks.

1. Ferrous iron .

If the specimen contains sulphides,by the Mit

scherlich method described in the text, these have a

tendency to reduce the ferric compounds to ferrouscompounds

,thereby giving too high a result in ferrous

i ron . This defect is remedied by a method devisedby J . P . Cooke . The rock powder is decomposed onthe water-bath, in an atm osphere of carbon dioxide,with sulphuric and hydrofluoric acids . A water-batheight inches in diameter has perforations in its small

est rings . The outer ring contains a groove,which

can hold a little water to make an air-tight j oint witha glass funnel . There are two tubes on the sides Ofthe bath, through one of which a stream of carbondioxide flows from a generator. (Fig.

A gram of the rock powder is weighed into a platinum crucible of 4 -50“ capacity, and 10“ of dilutesulp huric acid are slowly added . The crucible isplaced on the water-bath, which is heated to boiling.

A glass funnel with the stem cut 0 5 i s placed in the


groove, and the stream of carbon dioxide is introduced .

By means of a platinum funnel with a long stem for a

sti rrer, 10“—20“ of hydrofluoric acid are added .

The bath is kept boiling for half an hour, when it is

allowed to cool, the stream of carbon dioxide continuing. The contents of the beaker are washed into aplatinum dish and titrated with a standard solution

of potassium permanganate .

2. The J . Lawrence Smith method of estimatingthe alkalis .

A half gram of the material is sufficient for this de

termination . The fine powder is mixed in a platinumcrucible with the same weight Of ammonium chlorideand eight times as much alkali- free calcium carbonate .

The crucible is then heated to bright redn ess for anhour . The cold crucible and its contents are placedin water in a porcelain evaporating dish

,and boiled

for som e time, after crushing to a fine powder . Thisdissolves the alkalis with som e calcium hydrate. It isfiltered, the precipitate is discarded, and solutions of

ammonium carbonate, amm onia, and a few drops ofam m onium oxalate are added . Allow the substance tostand a few hours, filter into a platinum dish, evap

orate to dryness, and heat the residue sufficiently torem ove the ammonium salts .

Dissolve the residue in a little water . I f the rockcontains sulphides, add a few drops of a solution ofbarium chloride to precipitate the sulphates . A littleammonium carbonate solution is next added to precip itate the barium, and the trace of lime which m ay


be present. If there are no sulp hates, a few drops

of a solution of ammonium oxalate are added, whichprecipitates lime more completely than ammonium

carbonate . Filter, and to the filtrate add a few dropsof hydrochloric acid and evaporate to dryness in a

weighed platinum dish . This gives the potassium

and sodium chlorides . The potassium chloride can beseparated from the mixture as described on pages80-81, and the sodium chloride can be determined bydifference .It may be well to m ake a blank test wi th the am

m on ium chloride and calcium carbonate for alkalis,and to apply any necessary correction .

3. To prepare the ammonium molybdate solution,used to precipitate phosphoric acid.

Dissolve 75 grams of ammonium molybdate in 500cc

distilled water,with the addition of a little ammonia,

i f necessary. If the solution is not clear it shouldbe filtered and then poured, with constant stirring,into a mixture of 250“ of concentrated nitric acid(Sp . G and 250“ distilled water. The freshlymade molybdate solution must be allowed to stand ina warm place for several days . The clear solution isdecanted or filtered for use. The solution will keeponly a few months, as the molybdic acid is slowlyprecipitated . This is an expensive reagent andshould not be wasted .

PART III .

VOLUMETRIC ANAL" SIS .

VOLUMETRIC analysis consists in adding from aburette a solution of known strength, called thestandard solution, to a known quantity of substancein solution, until a definite reaction, as shown by anindicator, takes place. From the amount of the

standard solution added,the percentage sought can

be determ i ned .

Indicators.

The chief substances used as indicators are litmussolution, which turns blue in contact with alkalis andred with acids ; phenolphthale in solution, which iscolorless in acid solutions and red in alkaline solutions ; methyl orange solution, which is reddened byacids, and made yellow by alkalis ; and neutral p otassium chromate solution

,the indicator used in titrating

the halogens with silver nitrate ; and starch solution.The solution of phenolp hthalei

’

n is made by dissolving two grams of the crystals in 150“ 95 per cent

alcohol . The theory of indicators is discussed in

some of the larger manuals .

81


General Remarks and Suggestions.

I f only one determination is to be made, the gravimetric method would doubtless be chosen. If a num

ber of similar determ inations are required, the volumetric method is more expeditious, especially whenthe standard solution has been made and its valuedetermined .

The burette, so important in volumetric analysis,consists of a straight tube of uniform bore

,gradu

ated into centim etres and tenths . By a little practice,

the hundredths can be estimated with sufficient se

curacy.

The Geissler form of burette is probably the mostconvenient. In this the solution i s delivered through

a glass stopcock . The stop cock should occasionally

be rubbed with a little vaseline to secure easy actionand close fitting.

The burette should be cleaned with fuming nitricacid, or p ulverized potassium bichromate and sul

p huric acid . Frequent cleanings are necessary whentitrating with potassium perm anganate .

Rinse two or three tim es with the standard solution before beginning the titration . In reading, hold

the burette loosely between the thum b and forefinger,

that it may assume a vertical direction . With the

eyes on a level with the upper surface of the liquid, to

avoid parallax, read each time from the top of the

meniscus . It is not necessary to use a float.*

Zeitschr. angew. Chem ie x v. 4.


To seeni e accurate results in volumetric analysis,even greater carefulness is demanded than by thegravimetric process . The weights of the substancesemployed for the standard solutions must be determined with the greatest possible accuracy.

1. Titration with potassium permanganate.This reagent oxidizes the substances . Other ox idiz

ing agents sim ilarly employed are potassium bichro

mate, potassium ferricyanide, iodine, and ferric chloride .

To prepare the solution .

Weigh 5 grams comm ercial potassium permanga

nate on the rough balance . Dissolve in hot water

and dilute to a litre . Keep the solution in a darkplace, and each time after using withdraw into themain portion any residue in the burette .

*

If chemically pure potassium permanganate werealways at hand, the value of a centimetre of the solution could be determined by a simple mathematical

Professor H . N. Morse and students of Johns HopkinsUniversity have investigated the cause of the deteriorationof perm anganate solutions. They conclude that it deteriorates ou account of the form ation of m anganese dioxide inthe solution. If carefully filtered through asbestus or glasswool, it does not deteriorate in the dark or in diffused daylight. The case is different in direct sunlight. The solutiononce p laced in the burette should be filtered before returningto the m ain p ortion. Careful attention to these details d is

p enses with the frequent determ ination of the strength of thesolution . (See The Am erican Chem ical Journal xvi ii .

VOLUMETRIC ANALYSIS 95

calculation . It is well, however, to become accustom ed to working with impure materials .

The two main reactions with permanganate titrations are

A. l OFeSO, 2KMnO, 8H,SO,K,SO, 2MnSO, 8H,

O .

B . 5FeCl2 KMnO, 8HCl 5FeCl, KCl +1MnCl

2 4H,O .

Accurately weigh six or eight pieces of the purestpiano wire,* .12 of a gram in each . Wrap eachportion with a piece of paper, on which its weight is

written . Place them in a desiccator until needed .

The wire should contain of iron, but the

amoun t can be gravimetrically determined.

Two portions of wire at a time are dissolved in

four-ounce flasks having a bulb tube, valve, and plugsimilar to that used in determining the ferric oxidein Siderite on page 39. Dissolve the iron in dilute

sulphuric acid, hastening the action by gentle heat.The flask should be inclined at an angle ofWhen all is dissolved, heat for a moment to boilingto expel the hydrogen, which has power to reduce

perm anganate solution . Cool and wash the contentsof the flask into a litre beaker . Add 50“ of dilute

sulphuric acid and dilute each time with water to 1}of a litre . The water used in these determinations

should be freshly boiled to expel oxygen . Place the

beaker on a piece of white paper and add perm anga

Rem ove any oxide on the wire by rubbing it with sand

p ap er.


nate solution from the burette until a light pink colorremains a mom ent or two in the liquid . The perman

ganate thus serves as an indicator, and no other isnecessary.

In this way ascertain the amount of iron that cor

responds to a cubic centim etre of the solution, andcontinue until two consecutive results agree to the

fifth decim al place .An illustration :

(1) 1“ of the solution corresponded to CIOIOFe

(2 ) l“

00881“

(3 ) l“ 00805

(4) l“ 00785

(5 ) 1“ 00798

(6) 00800

(7) l“ 00802

(8) l“ 00802

When the value of the solution is determined the

rest follows easily .

I. TO determ ine the percentage of iron in siderite,FeCO,

.

Two different tests are made in all these determinations .A half gram of the finely pulverized substance is

placed in each of the two flasks, dissolved in dilute

hydrochloric acid, and treated in every respect likethe piano wire . Cool , wash into a beaker glass, andadd 10“ of a solution of manganese sulphate to



(a) Fezo,

(b)

4. Haematite, FezO, .

Proceed as in lim onite .5. Magnetite .

Composition : FeO,Fe,O,

.

(a ) To determ ine F80 .

Place a half gram of the pulverized substance ineach of the flasks, and dissolve it in dilute hydro

chloric acid . Heat to boiling until the silica is white .

Cool, and transfer to a beaker with 10“ of manganese sulphate solution

,and titrate .

An analysis showed :

FeO

(b) To determ ine the total am ount of iron .

Treat as in (a ) . When all is dissolved,reduce the

iron with pure zinc, and titrate as usual .Knowing the am ount of FeO and the tota l amount

of iron, the percentage Of FezO,can be determined .

An analysis showed

62 .51fl Pezo,

6. To determine the purity of black oxide man

ganese (M110 2 ) .


Dissolve .4 gram of piano wire in the flask with

dilute hydrochloric acid,and remove the hydrogen by

boiling. Cut 14cm from the bottom of a test-tube,and 2cm from an ordinary glass tube closed at one

end. A piece of platinum wire is wound around theportion of test-tube, while an end of the wire is m ade

into a loop for suspending on the balance . The glass

tube is placed in the test-tube . Weigh into the inner

tube .2 gram of the manganese dioxide . Place this

tube and its contents in the iron solution, and heat

until the silica that may be contained in the m anganese has becom e white. Then wash the contents ofthe flask into the beaker, add the m anganese sulphate

solution, and titrate as usual .

Make the com putation as follows : Multiply the

num ber of centim etres of the permanganate solution

used by its value . Subtract the product from theam ount of piano wire taken . The difference is the

quantity of iron oxidized by the m anganese dioxide

employed.

2Fe is oxidized by Mn0 2 ; or in the ratio of 112to 87 . Multip ly the foregoing difference by and

divide the product by the weight of the m anganesediox ide used, to find the percentage required .

Two analyses resulted

(a) MnO,

(b)

7 . KNO,.

To determ ine its purity .


Place in a half-litre flask a gram of piano wire .

The flask is fitted with a two-holed rubber stopper,into which proj ect glass tubes, bent at right angles .One tube is closed with a piece of rubber tubing andglass plug ; the same is on the end of the second tube,the rubber connection containing a slit for the escapeOf gases .

Dissolve the iron in dilute sulphuric acid and heatto drive off the hydrogen . Cool in a dish of water,with a stream of carbon dioxide passing through theflask . Then quickly introduce into the flask .2 gram

of potassium nitrate weighed as the m anganese diox

ide in 4. Boil the contents of the flask ten or fifteen

minutes, while a stream of carbon dioxide passesthrough . Continue until the dark green color dis

appears and a lighter yellowish-green results .Cool in a vessel of water as at first. Pour the con

tents of the flask into a beaker and titrate as usual .Compute as in the case of manganese dioxide

,re

m em bering that SFe is oxidized by KNO,.

Analysis resulted :

(a ) KNO,

(b)

Remarks.

1. The method of standardizing the potassiumperm anganate solution with iron wire is known asMarguerite ’s m ethod . Ferrous ammonium sulphateand oxalic acid are used for the sam e purpose.


II. Titration with potassium bichromate .

The molecular weight of potassium bichromate is294, and in acid solution it yields 48 parts by weightof available oxygen, as follows : 4H,SO,KzSO4

4H,O 30 .

As eight grams of oxygen are equivalent to one

gram of hydrogen, a norm al solution of potassium bi

chromate will contain eight gram s of available oxy

gen . This would require one-sixth of the molecularweight, or 49grams per litre.

Weigh six or seven grams of the pulverized bi

chrom ate on the rough balance, and dry as describedin the analysis of potassium bichrom ate, page 22 .

To prepare a deci-normal solution, weigh out exactly

grams of the dried salt and add sufficient waterto make a litre of the solution . If a pure salt is used,which is quite easily obtained, it is not necessary to

standardize the solution . The oxidation of ferrous

iron to ferric iron by potassium bichromate is shownby the following equations

oreso, K,Cr

,O, 7H280 .

Kzso4 7H20

6FeCl, x ,Cr

,o,14HCI= 6FeCl,

2CrCl, m m 7H,O

It is thus shown that 294 gram s of bichromate ox idizes 336 grams of ferrous to ferric iron, and

grams of the salt would oxidize grams of iron .


A cubic centimetre of the solution would therefore

oxidize gram of iron .

To find the percentage of iron in any given specimen .

Multiply the number of centimetres required inany given analysis by and divide the productby the weight of the ore taken .

It is not necessary to use manganese sulphate inthe titrations with potassium bichrom ate .To find the end of the reaction .

Place twenty or thirty sm all drops of distilled

water upon a white-glazed porcelain tile,and touch

each drop with a crystal of potassium ferricyanide .

(The crystal m ust be free from potassium ferrocy

an ide, ) The ferricyanide gives a blue color wi th

ferrous salts,but not with ferric salts . The bichro

m ate solution is carefully added from the buretteuntil the blue color exactly disappears . The same

substances that were determ ined with the perm anganate solution can now be determ ined with the bichro

mate solution and in the same order . Write the equa

tions that express the reactions in each analysis .

III. Titration with silver nitrate . Exercises in

the preparation of normal solutions .To prepare a one-tenth norm al solution, a deci

normal solution, of silver nitrate .*

A norm al solution of Silver nitrate contains 170 gram s

of the salt dissolved in a litre of water (notice that 170 isthe m olecular weight) .A norm al solution as defined by Mohr contains in one litre


Pulverize 18 gram s Of silver nitrate, and dry it inthe air-bath at 110 °

to constant weight. Weigh out17 gram s of the dry powder and dissolve in a litreof water .

Place about two grams chemically pure sodiumchloride in a porcelain crucible, heat to melting witha blast lamp, i f necessary, to remove all moisture .

Let cool in a desiccator, crush into sm all pieces, andtransfer to a weighing tube .

Weigh out .10— . l 5 gram of the salt in a 200

glass bottle, with a closely fitting ground stopper .

Dissolve the salt in 80“ of water and add a cubiccentim etre of nitric acid, which assists in collecting

one equivalent of the active reagent in gram s. The equiva

lent in gram s has been defined as that quantity of the

active reagent wh ich contains, rep laces, unites with, or inany way directly or indirectly brings into reaction one gramof hydrogen.

" A norm al solution of hydroch loric acid wouldcontain gram s of the gas to the litre ; wh i le one of

sulphuric acid would contain 49 gram s, half the m olecularweight, as sulphuric acid contains two atom s of replaceablehydrogen .

To p rep are pure sodium chloride : Make a strong solu

tion of the best com m ercial sodium chloride obtainable, andsaturate with Hcl gas, obtained by heating the strong com

m erciai hydroch loric acid. The delivery tube should term i

nate in a glass funnel, the m outh of wh ich should p rojectinto the salt solution, to p revent a clogging of the tube. The

pure salt will be p recip itated. The m other liquid should bedrawn from the p recip itate with a filter p um p , the salt

p ressed between filter pap ers, and heated in an evaporatingdish to remove hydrochloric acid.


stoppered bottle of 200“ capacity, add water and a

very small piece of sodium chloride. The salt servesas an indicator. Add silver nitrate to the warm solution until a precipitate forms . AgCN is soluble in

HCN , and no precipitate of AgCl will appear unti lthe HON is exactly neutralized . The precipitate

AgCl is more plainly seen than AgCN .

To prepare a normal solution of hydrochloric acid .

This should contain grams of the gas to a litre

of water.Into a bottle with a glass stopper, of 10“ capacity,

weigh a half gram of the dilute hydrochloric acid to

be found on the laboratory shelves . Transfer the

hydrochloric acid to the glass-stoppered bottle beforeused . Dilute to add nitric acid

,and use the

silver nitrate solution as in the common salt.

Suppose the acid is found to contain ofHCl gas, which would be parts in 1000. Then

" the m ol .w. of HG] : Take

therefore gram s of the dilute acid and dilute

with water to a litre .-If this should not prove a nor

mal solution, add water or the dilute acid as the casemay require .

By the use of the one-tenth normal silver nitrate solution, mhke one-tenth norm al solutions of potassium

bromide and potassium iodide ; also of sodium bromideand sodium iodide.


Alkalimetry.

In these determinations, litmus solution is used as

an indicator. It is prepared as follows : Boil ten

grams of powdered litmus in 100“ of distilled water.Filter, and divide the filtrate into two portions . Onepart is weakly acidified with nitric acid and the twoportions are mixed . Add two drops of the solutionto 200“ of water and test the sensitiveness with a

drop of acid.

When litmus is used as an indicator in determiningthe alkaline carbonates, as the CO2

acts upon the lit

m us, the liquid must be boiled to expel the gas . Thealcoholic solution of phenolphthalei'n can be used inmost determinations in alkalimetry and acidim etry.

When used, boiling to expel the CO2 is not necessary.

With the norm al solution of hydrochloric acid determine the strength of the ammonia water on the

laboratory shelves . Analyze also the various samplesavailable of sodium carbonate and bicarbonate, p otassium carbonate and bicarbonate

,and lithium carbo

nate, and ammonium carbonate . Boil the solutions

to expel the C0 2, which is liberated on the additionof hydrochloric acid .

To make a normal solution of caustic soda .

In the small glass bottle, weigh about .5 gram of

the solution at hand . Dilute this in the large beakerwith 200“ of water, previously boiled to expel theCO

, which distilled water sometimes contains. Us


ing the litmus solution as an indicator, titrate with thenormal hydrochloric acid . Having determ ined the

strength of the caustic soda solution, the normal solution is made from it, as in the case of hydrochloric

acid .

In the same manner,prepare a norm al solution of

caustic potash .

Acidimetry.

With the normal solution of caustic soda, determinethe strength of the sulphuric, nitric, hydrochloric, and

acetic acids that are used in the laboratory . Make

norm al solutions of all the acids,using both the nor

m al solutions of caustic soda and caustic potash .

With the norm al solution of sulphuric acid, using

methyl orange as an indicator, which is not affected

by CO,,determ ine the purity of the various alkaline

carbonates at hand . Com pare the results with thoseObtained from the norm al hydrochloric acid.

IV. Iodimetry.

To prepare the reagents .

(a) Iodine solution .

Weigh between two watch-glasses held together bya clamp 5 gram s of com m ercial iodine . Add this to

12 gram s of potassium iodide dissolved in 25“ of

water and dilute to a litre . Before use, it should bewell shaken to form a hom ogeneous mixture.


dishes . Pulverize the sublimate and let it stand in a

desiccator, over sulphuric acid. The desiccator

should be free from fat.

To determine the value of the iodine solution

( solution a) .

Place in a large beaker one measure of the diluteH

,SO, solution . Rinse the bottle twice with water .*

With the beaker standing on white paper, add acubic centimetre of the starch solution

,and the

iodine solution from a burette until the blue color

appears .

Secondly,place another measure of H

,SO, solution

in the beakers,and add to it .15 gram of iodine from

the desiccator . Titrate with the iodine solution until

the blue color is seen . Subtract the amount of theiodine solution now required from the amount whenonly the H,SO, was used . Divide the amount of

iodine taken by the difference and the quotient is thevalue sought .

1. To determ ine the strength of a solution of sulp huretted hydrogen.

Take 25“ of dilute H,S water, add a few drops ofthe starch solution

,and titrate with the iodine solu

tion.

Reaction : H,S 21 2HI S17 : 127

Multiply the number of centim etres of the iodinesolution taken by the value

,and the product by11237 .

The distilled water used in connection with H2SO

3

should be boiled to exp el oxygen.


then by 4 to get the number of parts in 100, or thepercentage of H,S .

2. To determ ine the degree of purity of sodium

thiosulphate, 5H,O .

Dissolve a gram of the substance in water, add thestarch solution as usual, and titrate with the solution

of iodine .

Reaction5H,O 21 2NaI

5H,O I 248 127Multiply the number of centimetres of the iodine

solution employed by fi -Q and divide the product bythe amount of sodium salt taken to find the percentage.

3. To determine the degree Of purity of potassiumiodide .

In the analysis, chlorine water is used (one part ofa saturated solution of chlorine and one part water ) .

ReactionKI 6Cl SH

,O HIO

, KCl 5HCl

The value of the chlorine water is determined at

the beginning and end of the analysis, and the average of the two results is used . The following is the

method

25“ of the chlorine water is placed in a largebeaker glass. A measure of the H,SO,, som e crystalsOf KI, and starch solution are added. Titrate with

the solution of iodine .

About .2 gram of the potassium iodide is dissolvedin water in a cylinder with a good glass stopper. A


little carbon disulphide is added. From a burette,chlorine water is dropped into the cylinder until theviolet color is removed .

The com putation : Multiply the value of the iodine

solution (a) by the quantity of the solution equivalent

to 1“ of the chlorine water . This gives the value ofa (alpha) , which is the iodine equivalent to 1“ of thechlorine water .

Multiply the value of a by one-sixth of the number

of centimetres of the chlorine water required for the

quantity of potassium iodide used . Multiply the

product by and divide by the weight of potassiumiodide taken to find the percentage required.

KI I 166 127 H 1Two analyses resulted

(a) KI(b)

4. To determine the purity of potassium bromide .

A small portion of the substance is dissolved in a

porcelain evaporating dish, heated to boiling, andkept at that temperature while chlorine water isdropped from a burette until the yellow color hasdisappeared . Find the value of a and computeas in the case of potassium iodide.Two analyses resulted :

(a) KBr

(6)


Weigh out .1 gram of the manganese dioxide,place it in the flask, and add 50“ dilute hydrochloric

acid . The retort should contain about 100“ of a tenper cent solution of potassium iodide . The flask andretort are connected and a stream of CO, introducedinto the flask to drive out the air.* The flask is then

heated, and about 25“ is allowed to distill into the

retort. The liberated chlorine sets free the iodine of

the potassium iodide . The contents of the retort are

poured into a beaker, allowed to cool, and one or twomeasures of H,SO, are added, suflicient to make theliquid colorless . The liquid is then titrated with iodine solution, the starch being used as an indicator.

From the amount of the iodine solution necessary thepercentage can be com puted as follows : Subtract thenumber of centimetres of iodine solution used fromthe iodine equivalent of the H,SO, and multiply thedifference by the value of a . The product Obtainedshould be multiplied by 2

3511.

Reactions : MnO,4HCI MnCl 2H,O

Cl, . 2KI 2Cl 2KCl I,

. MnO,is the equiva

lent of 21. MnO,2I 87 254.

An analysis resulted :

(1) MnO,

(2)

7. To determine the purity of potassium bichrom ate,

The use of C02is not absolutely essential in the deter

m ination.


The m ethod and apparatus are precisely similarwhat was used in 6.

Reactions : K,Cr

,O, 14HC1 7H,O 6Cl

2KCl 2CrCl,.

6C] 6KI 6KC1 61.K,Cr

,O, 61 294 762


( I) 99-955 c rzor

(2)

PART IV .

THE ANAL" SIS OF ORDINAR"

DRINKING WATER.

To prepare the solutions.

(a) The lime-water.

Take 200 grams of freshly burned lime, add a little water, and when decomposed add water until it is

about the consistency of cream. Let it settle, and

decant the clear liquid into a large bottle . It shouldbe filtered before using.

(6) The one-tenth norm al solution of silver nitrate.It can be made with sufficient accuracy for these

analyses by dissolving 17 grams of the dry powderin a litre of water.

(0) The one-tenth normal barium chloride soluti on.

Dissolve grams of the pure crystals (BaCl,,2H

,O) in a litre of water.

(d) The neutral potassium chromate solution .

The commercial article should be entirely freedfrom chlorides by repeated crystallizations in water.D issolve ten grams of the pure, air-dried salt in a

litre of water.

(e) The solution of oxalic acid.

119


Dissolve grams of pure oxalic acid crystalsin a litre of water . Usually a cubic centimetre of

this solution will exactly neutralize a like volume ofthe lim e-water .

(f) The Nessler reagent.

Dissolve 175 grams potassium iodide and grams

of mercuric chloride in 400“ of boiling water . Whencool

,add a cold saturated solution of mercuric chlo

ride until a little of the red precipitate which forms

(HgI,) rem ains in the liquid. At first it is dissolved

as rapidly as it form s . Then add 80 gram s of solid

caustic potash and dilute with sufficient water to make

(g) The perm anganate solution .

Dissolve 200 grams of solid caustic potash and 8

grams of crystallized potassium perm anganate in twolitres of distilled water which is free from ammonia .

Distill 0 3 one litre of water from the solution, testing

the last portions of the distillate with the Nessler reagent to ascertain if all amm onia is removed . If not,add m ore water and continue the distillation . When

the operation is finished there should be a litre of thesolution .

(h) The stronger ammonium chloride solution .

Dissolve grams of pure ammonium chloride in

a litre of distilled water that is entirely free from am

monia . Prepare the water by repeated distillations,if necessary .

( i ) The weaker ammonium chloride solution .

Take 5“ of the stronger solution,to which add 495“


litre distilled water . Each cubic centimetre will contain one milligram of chlorine.(n) Phenolsulphonic acid .

Place 370 grams of pure concentrated sulphuricacid in a flask with 30 grams of pure phenol, and keepfor six hours in a bath of boiling water. The reac

tion

C,H,OH 2H,SO,

( 0 ) Standard potassium nitrate solution .

Dissolve gram of pure KNO, in one litreof distilled water . Evaporate 10“ of this solution todryness on the water-bath . Thoroughly moisten the

residue with 2“ of the phenolsulphonic acid and di

lute to a litre . A cubic centim etre of this solutionwill correspond to milligram nitrogen .

The analysis of water .1. To determine the total amount of solid matter .In a cleaned and weighed platinum dish of 150“

200“ capacity,evaporate a litre of the water to dry

ness on the water-bath . Use pure water in the bathfor this evaporation, in order that matter from the

water may not collect on the outs ide of the dish .

Heat the dry residue to constant weight at2. To determ ine the silica .

Moisten the residue in the platinum dish with a

In water analyses the quantity in p arts is usually

estim ated. Therefore as 1000 p arts were taken in the be

ginning, m ultip ly th is and the following results by100.

ORDINARY DRINKING WATER 123

few drops of concentrated hydrochloric acid, and add50“ of water. Let it stand a short time and filter.Determine as usual .

3. To determine the i ron and alumina .

*

The filtrate from 2 is oxidized with a few drops offuming nitric acid, heated to boiling, and a smallquantity of ammonium chloride is added, and am

m onia to slight alkalinity . Boil to expel the excessof ammonia . Filter, and determine as usual.4. To determ ine the CaO .

Proceed as in previous cases.5. To determ ine the Mgo.

Evaporate the filtrate from 4 to smaller bulk andprecipitate with ammonium carbonate .6. To determine the sodium

,potassium, and lith

ium .

Evaporate the filtrate from 5 in a platinum dish todryness on the water-bath and with a free flame re

move the ammonium salts .

Dissolve the residue in a small quantity of water,and filter through a small paper into a weighed platinum crucible. Evaporate to dryness, heat to redness,cool, and weigh .

Having previously shown , with the spectroscope,the presence of lithium in the residue of an evap o

rated portion of the water, treat the substance in the

These are usually p resent in sm all quantities, and are

estim ated together. If, for any reason, it is desirable tosep arate them , it can be done, as in dolom ite, phosphoriteand granite, Part Second.


crucible with a mixture of equal parts of anhydrousalcohol and ether. This dissolves the lithium chloride, but does not affect the potassium and sodium

salts .

Evaporate the alcoholic extract to dryness on the

water-bath, heat to redness, and weigh . If desirableto separate the potassium from the sodium, the method

is the same as in the case of granite, Part Second.

To determine the sodium,potassium, and lithium .

Second method.

Evaporate 500“ of the water to dryness in a platinum or porcelain dish

,add one-fourth of a gram of

barium hydrate and a little distilled water to the dryresidue, and heat to boiling. Filter and discard theprecipitate . The filtrate contains the alkalis as chlorides and nitrates . The excess of barium is removed

with a little ammonium carbonate solution. The pre

cip itate is discarded, and the filtrate is evaporated todryness in a porcelain or platinum dish. The residue

is carefully ignited on the addition of a little solid

ammonium chloride to change to alkali chlorides. A

little warm water is added, and the substance isfiltered through a small funnel into a weighed plati

num or porcelain crucible . It is evaporated to dryness, and ignited on the addition of a little solidammonium chloride .

When the alkalis are determined by this process,the magnesium can be precipitated in the usual wayby sodium phosphate and ammonia

,which is often

the more sati sfactory process.


for the 10“ of the flask by fifteen (as there were150“ in the flask) , subtract the product from theamount of oxalic acid corresponding to the 45“ of

lime-water,and the difference is the quanti ty of CO2

in parts of the water.

10. To determine the free ammonia.Place 500“ of the freshly drawn water in a litre

flask connected with a Liebig condenser and distilloff Before begi nning the work, distill purewater through the apparatus for two hours to remove

all the ammonia .

Place 50“ of the distillate in one Nessler glass andthe same quantity of pure disti lled water in another.Add to each 2“ of the Nessler reagent ; and the diluteammonium chloride solution to the glass containingthe pure distilled water until it has the same color asthe contents of the other glass . Multiply the numberof centimetres required by four, and the product bytwo, to find the number of centimetres of the am

m on ium chloride solution that would be required fora litre Of water . All the free ammonia in 500“ ofwater will be contained in the 200“ of the distillate.Reaction

2 (2KI, HgI,) NH, 3KOH NH,HgOHgI

7KI 2H,O

11. To determine the album inoid ammonia .

To the 300“ of water remaining in the litre flask

It should be drawn not m ore than twenty-four hours at

the longest before the determ ination is m ade.

ORD INARY DRINKING WATER 127

add 50“ of the perm anganate solution, and again

distill ofi'

This distillate contains all the album inoid ammonia transformed by the permanganatesolution into free ammonia. Nesslerize 50“ as in

10.

According to Wanklyn the potability of water isdetermined by the quantity of albuminoid ammonia itcontains . He says : Albuminoid ammonia above .10per million begins to be a very suspicious Sign, andover .15 it ought to condemn a water absolutely.

When the albuminoid amm onia amounts to .05 , then

the proportion Of free ammonia becom es an elementin the calculation ; and I should be inclined to regardwith som e suspicion a water yielding a considerablequantity of free ammonia along with m ore than .05

parts of a lbuminoid am monia per million .

" Otherauthorities contend that a greater amount of the em

monias is permissible in a good water .

12. To determine the nitrates .

(a) Reduction to amm onia by nascent hydrogen .

Prepare 200“ of a solution of caustic soda free

from ammonia by adding cautiously and in sm all

pieces 4 grams of metallic sodium to 200“ Of good

distilled water.

Add 200“ of the water to be tested to the samequantity of the caustic soda solution , and into themixture introduce an excess of alum inum foil . Let

stand a number of hours .

Pour the liquid from the undissolved aluminum into

Water Analysis, p p . 67-68.


the litre flask, add 50“ of the permanganate solution

,

and distill ofi'

Nesslerize 50“ as in the deter

mination of the ammonias .

In case a large quantity of nitrates is present, itwould be more convenient to Nesslerize 5“—10“ ofthe di stillate, to which add sufficient di stilled water tomake 50“

From the results herein obtained, deduct the

amount of the ammonias ; and H of the remainderis nitric acid .

(b) The phenolsulphonic acid method .

Add 1-10“ of a saturated solution of sodium carbonate to 100“ of the water, and evaporate to dryness on the water-bath . The sodium carbonate prevents loss from the volatilization of free nitric acid .

With the dish covered by a watch-glass on accountof efi

'

ervescence, thoroughly moisten the residue with

2“ of the standard phenolsulphonic acid . It is di

luted w ith water,rendered alkaline with ammonia,

and poured into a Nessler glass of 100“ capacity .

Distilled water is added to the mark . The color iscom pared with other glasses containing varyingamounts of the standard potassium nitrate solution,each containing 5“ of strong ammonia water. Per

manent nitrate standards can be kept for some weeks .I f there is a high chlorine content in the water, there

should be added to each Nessler glass 8 quantity of

the standard sodium chloride solution equal to theamount found in the water.

Reaction


in nitric acid, and precipitate in the usual way witha solution of ammonium molybdate .Water m ay occasionally contain arsenic, barium,

manganese, copper, lead, and other substances . Forthe estimation of these and their significance

,the

student is referred to the special works on wateranalysis.

1. Chlorine .All waters contain a certain normal amount

of chlorine, usually as sodium chloride, whichvaries greatly in difi

'

erent localities . The amount

is quite high in waters near the sea-coast, and

in wells in such localities as Syracuse,N . " .

The time will doubtless come when each state willhave a chart of the normal amounts such as has al

ready been worked out for som e localities . An excessive amount of chlorine indicates sewage contamination . SO a considerable interest always attachesto this determination.

2. Nitrates .

These are more likely to denote the decomposition

of animal than of vegetable substances . Stoddartsays

,Natural waters can at most Obtain but from

1-10 to 2-10 gram of nitrogen as nitrates per im

perial gallon to parts per million ) , from

sources other than animal matter, and practically the

whole of the nitrogen of sewage m ay be oxidized into

ORDINARY DRINKING WATER 131

nitric acid without dimini shing the risk involved indrinking it."

3. Nitrites .

Mallet has reported upon the presence of nitritesin eighteen natural waters believed to be of good,wholesome character, collected from a great varietyof sources. His determinations show an average of

part nitrogen as nitrites per million parts of

water. Mason says his experience has been that theaverage amount of nitrites found in good waters is

very much less than the value given by Mallet. Considerable quantity of nitrites is sometimes found in

deep well and spring waters . They result from the

reduction of nitrates by ferrous salts or by organ icmatter which m ay have been imbedded for ages .4. Phosphates .These are usually found only in small traces in

good waters . If in considerable quantity, they indicate contamination, although there are known ex cep

tions to the rule.

5. As an aid to determining the purity of a drink

ing water,the source of the water and its surround

ings should be as carefully and thoroughly investigated as cipcum stances may permit. All availabledata should be considered in forming a judgment asto the potability of a given water .

The apparatus, chemicals, and minerals necessaryfOr this course can be Obtained of the usual dealers .For the most part, the articles will be found com

paratively inexpensive .

PART V .

APPENDI" .

Equations that exp ress som e of the m ore com p licated te

actions.

Total iron, FeO and Rezos.

Fe203

6HCl 2FeCl3

3H20 .

F 2H 1: F l O

P

e

g? +HCIC

11N°

d32 +1316? +1316 NOe

2 ae

a 9 2°

2FeCl3

3BaCO3

Fe (CO3)3

3BaClz.

Fe2(C0

3)3

6HCl 2FeCls

3BaClz.

BaCl2H280

4BaSO

42HCl.

FeCl SNH OH Pe (oH) SNH Cl.3 4 s 4

2Pe (oH) 8Re

zos

3H20 .

MnO .

BaCl2H

280

4BaSO

42HCl.

MuCO3

2HCl MnCl2H

20 CO

2

MnCl2 (NH4

)28 MnS 2NHq .

MnS 2HCl MnCl2HZS .

MnCl2Na

zCO

3MnCO

32NaCl.

17111003Mi lo C0

2.

3MnO O Mn304.

GERMAN SILVER.

(Page

Fe. SFe 8HNO3

3Fe (N03)2

4H20 2NO.

Fe(NOal)2

2HNO3

Fe (N03)3H20 NO

2.

135


2Fe(N02)2 +

3H2SO = Fe

2 4(SO )2 +

6HNO .

Fe (SOx°

- H Sz

2PeSO2

4 +H2S0

4 + S .

2FeSO4H256 + 2HNO:_— Fe

z

(SO + 2H2O +

2NO2

.

302

2H4 (COONa)

2 +Fe

2(SO ) 2

Fe2(C2H4)2(COO ) 2 + 8Na

2SO .

The ferric succinate6

heated becom es Fe202 + CO2 +

H20 .

Zn . = 3Zn (NO2)2 +

4H:Oa

+ 2NO .

Zn (N02)2H280

4= ZnSOH+ 2HNO

ZnSO4 +

2

Na C02_ ZnCO Na

2SO .

HCN + KOH— KCN + 2.O

ZnC02 +

2KCN = Zn (CN ): K200

2.

Zn (CN ) 2 K28 : Zns 2 .KCN

2

ZnS 2Hcl _2

,2

a H S.

ZnCl Na2CO

2

—_ZnCO2

2

.-1- 2NaCl

c d _ Zuo CO2.

SMALTITE.

(PageAs.

COAs 6HNO8

CO (N02)2

2H2AsO

44NO.

2112Aso

4 +5H

2

8

S : As2S4 +

2

8H2

AS2S4

3K2S _ 2K

2ASS

4

142414441844

40KOH 82Cl 4K280

482KCI 20H

4O

s8 4

Pot. arsenate.

The excess of KOH and Cl becom es2KOH 201: KClO1' KCl H

20 .

3KClO= KClO4 +

2KCl.

Adding dilute HCl.2HCl KClO : KCl 201 H

20 . The hypochlorite

and also the potassium carbonate are decom posed. The

Ferric succinate. fPot. hypochlorite.

138 QUANTITATIVE CHEMICAL ANAL"SIS

K28n0

3 2+ 3H SO = K==SO4 Su (SO4)2 +

3H20 .

2K P01+ 8HZSOZ= 3K280

H+2H P0

Sn SO ) +‘JH

2S : SnS

z

z + QH2SO .

Fluorine.

The m ethod outlined in the text was devised by BerzeliCa Na

2CO

8_ CaC0

3 +QNaF .

SiO2

2

2+ Na C03

8

= Na28i01+ C0

2.

Na2Si0

3 +2

(NH )2C0

3=

3

H2SiO

3Na

2C0 + 2NH .

The Si02is not completely

2

precipitated, therefore3

zincsulphate dissolved in ammonia is added.

No.2Sio

3 4+ ZnSO — Na2SO + ZnSi0

3, and at the same

time,2

2Na3P0 + SZnSO —_3Na

2SO + Zn

s(P0 )

2.

The phosphoric acid is thus precipitated . On evaporationthe excess of ZnSO and Na C0

3becomes ZnCO

3and

N a SO .

Qz

NaF + CaCl2- CaF

2 + 2NaCl. After acidifying thefiltrate with acetic acid, CaCl

2precipitates Ca in such

a gelatinous condition that filtration is possible only whena small quantity of calcium carbonate is precipitated withit by Na

2C0

3. After ignition, this CaCO

3is dissolved by

acetic acid,and the Ca is left in condition to be filtered.

Granite . (PageP205.

Ca3(P0

4)2 +

6HN03= $Ca (N0

8)2 + 2H

3P0 .

7H3P0

4 +12 (NH )

6

3

Mo 024 +

51HN03

)aP0

19191003

6H20 ]

6

51NH4N0

3.

7 (NH3P0

4 +12M00

379NH

‘0H 7 (NH P0

4 +19. (NH

6M0

7024+ 36 H

20 .

The ammonium phosphate is then precipitated with magnesia mixture as usual.There is a certainty only in the end products of theforegoing equations. It is not known exactly how the sub

stances combine in the original solutions.The chemically pure hydrop latinic chloride. (PageThe object of the treatment is to rem ove the two or

APPENDIX 139three per cent. of iridium that is usually contained inplatinum .

Hcl HNO3

C1 H20 NO

Z.

Ir 4Cl _ IrCl

QIrCl SNaoH 21r (0H)8

7NaCl NaClO +H20 .

Adding alcohol to the hot liquid,NaClO C

2H -H NaCl CH

s,CHO H

20 .

Ir (0H) 3 +2

3HC1: IrCl + 3H20 .

The iridious chloride is not precipitated by KCl, whilethe hydrOp latinic chloride is precipitated.

c2KCl H2PtCl K PtCl

6QKCL, PtCl

cIKCI, PtCl4

4H QKCl 4HCl Pt.Pt 4Cl 2HCl H PtCl

o.

The Pettenkofer m ethod of estimating the carbon dioxidein water .1. The ammonium chloride prevents the precipitation of

m agnesia by the lime-water. Such precipitation woulddiminish the alkalinity of the solution and cause an error .2. The CaCl sets free the weakly united (sem i-gebun

den ) C0 2, so that it m ay be determ ined . Carbon dioxidein a solution containing an alkali carbonate forms the

bicarbonate as followsNa

2 3C0 + C0 2 + H2

0 = 2NaHC08

2NaHC3

03 + C

z

aC12

—_ 2NaCl H20 C0

2CaCO

S.

3 . Why the difference m entioned in the2

text expressesthe CC in parts of the water.Suppose 45 cc . lime-water corresponds to 40 cc . oxalic acidsol., and 100 cc . water and 45 cc . lim e-water cor. to 31cc.oxalic acid sol.The C0 in the water makes a difference of 9cc. oxali c .100 cc . water contains g. C0

2.

cc. water contains 9g. C02

.

In this case 9cc. oxalic acid solution less is required because the CC in the water unites with som e Ca (0H)

2to

form CaCO The m ore C02the water contains, the more

Ca (0H)2would be withdrawn, and the less ox alic solution

140 QUANTITATIVE CHEMICAL ANAL" SIS

would be required . 1cc. of oxalic acid solution correspondsto 0.001g. C0

2. The 9cc. difference would correspond to

0.009g. C02, therefore, 100,000 parts of water would con

tain 9 p artz

s C02.

The Griess-Ilosvay reactions for nitrites in water.

+HN0 2= C HH/N

2 \O + 2H 0

\SOSH _ N

Sulphan ilic Acid. P . D

N

iazobenzene sulphonicanhydride.

2 \0 II‘

\N _—_N/ H/

m n la-Naphthylamine

H H H

/C (

ll

HL/C C

/\C C

/

IIc 1 1C aH

H C H H C

|C

ISOSH NH

2H

a-Azo amino naphthylic para benzene sulphonicThe substance which is of a pink color.

Perm anent standards. Where m any determ inations ofammonia are made, it is convenient to have perm anentstandards . These are prepared as follows


F igure 5 shows an apparatus for reading N esslerizedammonia tubes. The twelve standards are in the tubes

F ig. 5 .

APPENDIX

on the left, and the free and albuminoid amm onias are

in tubes on the right. The two sets can be rotated, untilthe colors on the left and right correspond. The am ount ofam monia per million parts of water that each tube corresponds to can be pasted on the outward metal cylinder. Theapparatus may be used for determining the amount ofnitrate in drinking water, when it is reduced to ammoniaby nascent hydrogen.


To find the weight of a given volume of gas.

W " V x (B— f)760 x (1 t)

W Weight of a cubic centimetre of the gas.

V Volume of the gas in cubic centimetres.

B The height of the barometer in millimetres .

f The tension of water vapor for the temperaturet,found in table 2.

00367 The coefficient of ex pansion of gas for

each degree Celsius.


TENSION OF WATER VAPOR.

FROM 0° TO 35 C.

Bunsen gasom etrisohe Methoden. 2d Ed . Page 357.

Tension0 Cels. 0 Cole. 0 Cele.

m etres.

APPENDIX 147

INTERNATIONAL ATOMIC WEIGHTS, 1915

ru n“1"1101.

A lum inium .

AntimonyrgonArsen ic .

BariumBism uth 0 0 0 0 0 0 0 0 0 0

BoronBrom ineCadm ium .

CaesiumCalciumCarbonCeriumChlorine.

Chrom iumCobalt .Colum biumCop perDysp

rosmm

ErbEurop iumF luorineGadol inium .

Gal l iumGerm an ium

G lucinumGo

Iod ineIrid ium

k-ou .

tryp on

LanthanaLo

LuteciumMagnesium .

Manganese"

Mercury .

ATOH'

IO

WRIGHTum :

u m ATOI IC

1101. wa ls er

MolybdenumNeodym iumNeonN ickelN iton

Osm ium

m

'

. II

PhosphornPlatinumPotassiumPraseodym iumRad iumRhodiumRubidiumRuthen iumSam ariumScand iumSelen iumS i l iconSi lver. .

SodiumStrontiumSulp hurTantalumTel lurium

Thal l iumThorium

ghulium

TungstenUraniumVanad ium" enon" tterbium" ttriumZ incZ irconium

150

Copper sulphate, p urifica

tion, 27Crucibles, manner of preparing, 8

Desiccators, 10Dolom ite, analysis, 32Dolom ite, composition, 32Dolomite, result of analysis,33

Dolomite, separation of ironand alumina, 34

Drinking water,119

analysis,

E vaporation, 11

F ahlerz, analysis, 59Fahlerz, composition, 59Ferric oxide, determination,39

,97, 98, 123

Ferrous oxide, determination, 32, 39, 82, 84, 98

F ilter ashes, to determineweight, 18

F iltering,6

F ilter papers, folding the, 6Filter papers, preparation,17

F ilter papers, to dry to constant weight, 55

F ilter papers, to remove inorganic matter, 17

F iltrate,to test, 7

F luorine, determination, 66

Gases, weight of a litre, 145German silver

, analysis, 48Germ an silver, composition,48

Germ an silver, reactions,135Germ an silver, result ofanalysis, 52Gooch crucible, 22

INDEX

Haematite, the iron by permanganate, 98Hydrochloric acid, normalsolution, 106

Hydrogen sulphide, determination, 110

Lead, determination, 42, 48,53, 63

Liebig’s method for hydro

cyanic acid,105

Liebig’s method for nickel,

56

Lime-water, preparation,119

Granite, analysis, 72Granite

,composition, 72

Granite, preparation ofpowder, 72Granite

,reactions

, 138Gravim etric analysis, 17Gravimetric analysis defined

,

17Griess-Ilosvay reactions,129,

Iceland spar, analysis, 28Iceland spar, composition,28

Iceland spar, result of analysis, 31Igniting the precipitate, 9Indicators

,91

Introduction,3

Iodimetry, 108Iodine, pure, preparation,109Iodine solution, preparation, 108Iodine solution, to determine value

,110

Iron, determ ination, 36, 40,44, 49, 56, 64, 70, 77, 82,123

INDEX

Limonite,the iron by per

manganate, 97Lithium

,determination

,123,

124Litmus solution, preparation

,107

Magnesia mixture, preparation

,46

Magnesium oxide, determ ination, 25, 33, 39, 44, 59,64, 71, 78,123,124Magnesium sulphate, analysis, 24Magnesium sulphate, resultof analysis, 26Magnetite, composition, 98Magnetite, the iron by permanganate, 98Manganese dioxide, analysis,98, 113Manganese oxide, determ i

nation of, 38, 64

Manganese sulphate in permanganate titrations, 101Marguerite’s method ofstandardizing

,100

Mercuric oxide, dry, preparation, 41Mercury, determination, 64M ineral analysis, preparation of material, 28

Mitscherlich m ethod for ferrous iron, 82Molybdenum, determination,76

Morse, Professor H. N 94

Naphthylam ineride, 121

Nessler reagent,tion,120

N ickel, determination, 51,56

,64

hydrochlo

prepara

151

N ickel hydroxide, washing,52

N itrates, determination, 127,128

N itrates, significance in water,130

N itrites, determination, 129N itrites, significance in water, 131

Normal solution, causticsoda

,preparation, 107

Normal solution, hydrochloric acid

,preparation,106

Normal solution,Mohr’s def

inition, 103

Oxalic acid solution, preparation, 120

Oxidizing agents, 94

Permanent standards,,140Permanganate alkali solution, 120Permanganate titrations, reactions, 95

Pettenkofer’s method, car

bon dioxide, 125, 139Phenol sulphonic acid, preparation, 122Phosphates, determinationin water, 129Phosphates, sign ificanCe inwater, 131Phosphoric acid, determination, 46, 69, 73Phosphorite (Apatite ) , analysis, 66

Phosphorite, composition of,66

Phosphorite, reactions, 137Platinic chloride, preparation, 83Platinic chloride, reactions,138

152

Platinum, care of, 12Platinum , removing stains,12Platinum solution, 141Potassium, determination,22, 78,123,124Potassium bichromate

,an

alysis, 22Potassium bichromate, reaotions

,102

Potassium bichromate titrations, 102Potassium bichromate, to determine its purity, 114Potassium bromide, analysis,112Potassium chromate, neutralsolution, 119Potassium iodide, analysis,111Potassium nitrate, standardsolution,122Potassium nitrate, to determine its purity, 99Potassium permanganate titrations, 94

Potassium sulphide, preparation

,51

Preci

gtates, filtering and

we ing, 6Precipitates, heating and ign iting, 8

Precipitates, how obtained, 5Precipitates, manner ofwashing, 7Precipitates, removal fromsides of beaker, 7Precipitates, to dry, 8Precipitates, to protectfrom dust, 8Precipitates, transference tofilter, 6

Reactions, 18Records,13

INDEX

Reduction with hydrogensulphide, 101

removal

Siderite, analysis, 86Siderite, composition, 36Siderite, determ ination ofits iron, 96

S iderite, reactions, 135Silica

,determ ination, 29, 32

33, 34, 86, 42, 53, 63 , 6874,122

Silver chloride,from crucible, 20

Silver coin, analysis,18Silver coin, composition,18Silver coin, result of analsis, 21

Si ver, determination of, 19,63

Silver halides by Goochmethod, 22

Silver, metallic, changed tochloride, 21

Silver nitrate titrations, 103

Silver nitrate, to preparedecinormal solution, 103

Smaltite, analysis, 52Smaltite, composition, 52Smith, J . Lawrence

,method

for alkalis, 86Sodium carbonate, dry, preparation, 41

Sodium chloride,pure, prep

aration of, 104Sodium, determination, 123,124

Sodium nitrite, standard so

lution, 121Sodium oxide, determination,81

Sodium phosphate,analysis,

46

Sodium phosphate, result ofanalysis, 48

· preface. in the following pages methods for complete an alyses are outlined, and substances...

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