836 T H E J O U R N A L O F I N D U S T R I A L I .

contact with the small amount of hydriodic acid, which has been formed in the solution. The reduction can be seen in the rapid return of t he blue color. This re turn of t h e blue continues only until the iodine in the hydroxyl has been completely liberated. An addition of j cc. of 2 0 per cent K I reduced the di-iodo- thymol bromide in one minute t o the di-iodo-thymol and t h e blue color does not return rapidly (i. e . , within m e hour) .

I n working with the cresols and phenol the blue did not re turn except in the case of t he ortho-cresol. The reading was taken after t he blue ceased t o re turn (j to I O minutes). However, it is advisable to use K I if the experiments show a tendency for the blue color t o re turn within five or ten minutes. The free hydriodic acid produced in the acid solution b y this addition reduces' t he thymol

. iodide completely, with one minute's shaking. Wilkie s ta tes t ha t his determinations were all high ( I ' , ' ~

per cent) . The explanation lies probably in the fact t ha t t he iodine is par t ly absorbed into the hydroxyl and as the iodo precipitate is filtered off in his method, there is no possibility of i ts reduction.

No K I was added.

D I R E C T I O N S F O R D E T E R M I N I h - G P H E N O L I C C O M P O L ' N U S

First . Solutions required: 0 . I rV sodium thiosulfate, 24.8 grams per l i ter ; 0.03 N iodine solution, 1 2 . 7 grams per liter; N sodium bicarbonate; 2 .V sulfuric acid; 0 . 5 per cent starch solution.

Second. In to a joo cc. ground stoppered bottle, pu t 50 cc. water and jo cc. of approximate N sodium bicarbonate, a d d I j cc. of t he unknown solution of the phenolic compound which has been previously diluted to approximately 0.1 N .

R u n in the iodine solution until the mixture in the bottle remains a permanent brown iodine color; LO

per cent excess is recommended. Stopper the bottle firmly a n d shake i t well for one minute .

Third. Add carefully, a t first, t o prevent excessive bubbling, jo cc. of 2 N sulfuric acid. Shake well a n d t i t ra te t h e excess iodine with the thiosulfate, using s tarch as indicator. Occasionally blue color returns rapidly after t h e end point has been first reached. For such determinations i t is best t o a d d j cc. of 2 0

per cent KI to hasten the freeing of t he iodine which-is held in the hydroxyl. The final end p o i n y a f t e r t he blue ceases t o re turn is the correct reading for t he thiosulfate. All the solutions should b e a t z 0 ' -2 5' ('.

S U &I M A R Y

I . Rapid and accurate determinations of 0-, m - , a n d p-cresol, phenol and thymol have been effected b y t h e use of iodine solutions in the presence of sodium bicarbonate.

11. T h e method is equally rapid and accurate for all five compounds, t he error for each compound being within 0 . 2 per cent.

111. The "reaction pey'iod" for these determinations is one minute, when the shaking is continuous.

IV. The s u m of t he cresols present in a mixture may be determined within a total error of 0.2 per cent . ;

1 Werner Jahresber , 6 3 3 (1886) Lloyd, J A m . Chem. SOL, 27, 16 (1905).

A N D E N G I N E E R I N G C H E M I S T R Y L'ol, 5 , No. I O

t he m-cresol may be determined in the presence of 0- a n d p-cresol b y this method.

Y. A series of simple equations are given which will permit the determination of phenol, meta-cresol and the s u m of the ortho- a n d para-cresols in the presence of each other in any combination or proportion if two quantit ies be known.

( a ) The weight of t he mixtures taken . ( b ) The amount of iodine absorbed. I T . Results of experiments are given which show

tha t these four compounds can be determined in the presence of each other b y this method within an error of 0 . 2 t o 0 .62 per cent, calculated on the sum of the materials present.

DEPARTMENT OF I N D U S T R I A L RESEARCH UNIVERSITY OF K A N S A S

LAWRENCE

AN APPARATUS AND METHOD FOR DETERMINING HY- DROGEN SULFIDE IN ILLUMINATING GAS'

By E. P. HARDINO AND EINER JIJHSSON

Received July 28, 1913

The apparatus herein described was designed as a means of testing the efficiency of a set of gas purifiers such as are used in the manufacture of coal gas or car- buretted water gas for illuminating purposes. I t combines the accuracy of the gravimetric cadmium chloride method and the rapidity of the 'I'utwilrr method.2

The appara tus con- sists of a bulb, A , of 300 cc. capaci ty about 18 c m . long a n d j cm. in d iam- eter, sealed a t t he lower end and con- t racted a t the top t o 13 mm. T o the con- t racted end is fused the tube G , termi- nating in a Greiner a n d Friedrichs s top- cock, D, t o which is fused burettes E and C, each having a capacity of I O cc. Buret te B is 20 cm. long and 1 3 mm. in diameter Cali bra ted in the middle por- t ion. C is 34 cm. long and I O m m . in diameter graduated into I O cc. a n d read- ing to ten ths of one cc. Both B and C are fitted with s top- pers. T o one side of bulb A a t L, 14 cm. from the base of A, is a t tached tube 'r 7 m m .

gress 1 Published iu abs t rac t in Proceedings of the 8 th Internat ional Con-

J . Am. Chem. Soc., 23, 173.

in diameter a n d terminating a t AI bearing a stop- cock. F, 2 j m m . from I,, a U tube, ], ;L bulh . 0, of I O cc. capacity and a bulb, P, 2 cc. in capacity. '1'0 the opposite side of bulb A a t H, I Z cni. from the ljase of A, is fused tube K 7 mm. in diameter beginning a t I and extending into the bulb and terminating a t N, 20 mm. from i ts base. E; bears t he stopcock E , , io mni. from H. S is a clamp which supports the apparatus . When passing gas through the apparatus i t is supportetl 1)y placing i t in a hole in a block of wood.

I n making a determination, from IOO i o 1 5 0 cc. of :i

strong solution of cadmium chloride are run into bulb -1, stopc.ock F being open and E closed. T h e apparatus is then tiltetl in such ;t position tha t j or 6 cc . of t h e solution pass into bulb C) which acts as a seal a n d indi- (,ator preventing traces of hydrogen sulfide from es- raping unabsorbed a n d indicating when the cadmium chloride solution in X is nearly spent. Bulb P prevents traces of solution in 0 from being carried from the apparatus .

Buret te C is filled with a s tandard solution of iodine, two solutions of different iodine strengths being used, one containing 4.828 grams of iodine per liter and another one-tenth as strong. The s t rong solution i s of such a s t rength tha t I cc. is equivalent t o I O

grains of hydrogen sulfide per IOO cubic feet when one- ten th of a cubic foot of gas is used in the determination and is used in testing t h e crude gas while t h e weaker solution is used in testing partially purified gas. Stop- cock D is closed a n d A is connected a t M with the meter a n d a t I with t h e gas supply cock by means of rubber tubing. The meter is read, E is opened and the flow of gas so regulated t h a t from I t o 1 . j cubic feet pass through t h e appara tus per hour. When a color appears i n bulb 0, t h e gas is shut off b y closing stopcock E a n d t h e meter reading taken . I n testing partially purified gas when no color has appeared in 0 after one-tenth cubic foot of gas has passed bu t when a perceptible precipitate has formed in A. t he gas supply is cut off. If a perceptible precipitate has not appeared in A after one-tenth cubic foot has passed, the flow is continued until one does appear .

The appara tus is disconnected from the meter a n d gas supply, removed from i t s support , D opened a n d then so t i l ted t h a t t h e solution in 0 runs back into A. Wash water is drawn in through 51 b y applying suction a t t op of B and through K by opening E, closing F :tnd applying suction a t t op of B . The gas above the solution in A is removed b y opening F a n d applying suction a t top of B. D is closed a n d fresh s tarch solution run into B , then D is opened a n d the s tarch solution r u n into A. E a n d F are closed and the air in ,4 placed under diminished pressure b y applying suction a t t op of B. D is then closed a n d B is filled with concentrated hydrochloric acid which is allowed to pass slowly into X until t he precipitate of cadmium sulfide is completely dissolved. A little excess o f , hydrochloric acid is then run in a n d I) closed. The hydrogen sulfide thus liberated in A under diminishecl pressure and out of contact with air is t i t ra ted with the iodine solution. Burette C is read and the iodine

solution introduced intermit tent ly by carefully opening D, the appara tus being shaken after each addition. When the starch-iodo blue color persists for one-half minute, t h e end point in the titration has been reached. (The pink or violet color which first appears in t h e solution must be distinguished from the starch-iodo blue which is t he correct end point . ) C is then read. The appara tus is then emptied, rinsed with water ant1 :L blank test run to determine the amount of iodinr solution necessary to produce t h e permanent starch- iodo blue color. I n making this test t he same amount of starch solution and the same Lrolume of water as i:: used in the determination is used and the wholr acidified with hydrochloric acid. From the amount of gas a n d the volume of iodine solution used i n thr determination a n d in the blank, t he number of grains of hydrogen sulfide per IOO cubic feet of gas is cal- culated. For control work the volume of gas used nvrtl not be reduced to i t s corresponding volume a t st:indartl conditions of temperature a n d pressure.

Comparat ive determinations of hydrogen sulfide were made b y the gravimetric cadmium chloride, the Tutwiler and the volumetric cadmium chloride meth- ods. I n these determinations the meters used were dry meters checked against each other, the samples were taken simultaneously and the volume of gas used reduced t o corresponding volume a t s tandard conditions of temperature and pressure liy means of t he following formulae:

1 i . 6 4 (h--- u ) ,

460 + t I C = ~ - -

y = 7J 17.64 (h-u) . 460 -t t

V = v n where V = volume of gas a t 6 0 " F. and 30'' pressure.

v = observed volume. t = observed temperature ;n Fahrenheit degrees.

12 = observed barometric pressure. u = tension of aqueous vapor a t t . it = correction factor for t a n d h.

The following results in grains, cadmium c.hloride, CdC12, per IOO cubic f-eet were obtained:

Grav.

2 . 7 2 0 . 5 3 0 . 8 9 1 . 5 8 1 .OO

1 . 3 1 2 .35

2 .68

Vol. Tutwiler Grav. Coal gas.

2 . 9 3 31 1.81 0 . 4 6 22 0 .88 0 . 7 9 27 4 . 8 6 1 . 5 4 , 38 2 . 7 3 0 . 9 2 24 1 . 2 2 2 . 6 5 30 2 . 7 2 1 . 2 5 23 1 .65 2 . 2 6 29 1 . 3 0

1 . 0 9

Vol Tutwiler Grav. Vol. 'I'utwiler Water gas

1 . 7 2 27 0 .5Y U . 5 5 16 0 . 8 4 18 0 . 2 6 0 17 8 4 . 7 6 110 0 . 4 0 0 36 I I 2 . 6 9 65 0 . 1 5 0 . 1.3 i 1 . 1 8 25 0 . 3 4 U 31 1 2 2 . 6 1 28 1 .59 3 0 225 .0 220 .0 .160.0 1 .26 26 lY0.0 188.0 310 1 . 0 4 24

Crude coal g a s

The uniformly higher results obtained by t h e gravimetric method may be due t o the absorption of other sulfur compounds t h a n hydrogen sulfide. a much larger volume of gas and cadmium chloride solution being used in the gravimetric method than in the volumetric method .

T h e principal advantage of Tutwiler's method is i ts rapidity. A test can be made in about t h r r e minutes. I t s chief disadvantage is i ts inaccuracy. The results obtained are only approximate especially

838 T H E J O l ' R n ' d L O F I I V D l ' S T R I A L

on the partially purified gas, the error varying from 1000 t o 4000 per cent as shown by the comparative tests above. This error is due t o the t i tration of t he gas with the iodine solution, the unsaturated hydro- carbons, cyclopentadiene' and probably sulfur com- pounds other t h a n hydrogen sulfide reacting with the iodine. Results on the crude gas are less inaccurate, t he error amounting to about I j per cent. This is of course due t o the much great,er ratio between the amount of hydrogen sulfide present and the other compounds with which the iodine reacts. SIcXIillar states in the original publication of Tutwiler's method tha t r j grains of hydrogen sulfide per IOO cubic feet of gas could escape detection. I n the writers' experi- ments, in no case did the Tutwiler show less t han i o grains per IOO cubic feet on clean coal gas nor less t han 4 grains per IOO cubic feet on clean water gas.

The gravimetric cadmium chloride method is t he most accurate in use a t the present t ime. The great objection t o this method, however, in control work is t he length of t ime required t o make a determination. The purifying boxes foul quite rapidly and in determin- ing their efficiency tests should be made rapidly and as nearly simultaneously a t inlet and outlet of purifier as possible. A method which requires hours for a test becomes impracticable. The large bulk of cadmium chloride solution used allows absorption of other sulfur compounds t h a n hydrogen sulfide, which when oxidized with the bromine give too high results. Another objection is the large amount of cadmium sulfide precipitate required t o produce an amount of barium sulfate which can be readily and accurately weighed. When a sample of 0.1 cubic foot of gas is taken. each milligram of Bas04 is equivalent to 2 . 2 j 2

grains of sulfur per IOO cubic feet. Thus for partially purified gas conta in ing-but a fraction of one grain of hydrogen sulfide per IOO cubic feet. a number of cubic feet of gas must be used in order to obtain a weighable precipitate.

T h e volumetric cadmium chloride method has several advantages over the gravimetric method. Accurate results are obtained on a much smaller volume of gas; a smaller volume of cadmium chloride solution causes less absorption of sulfur compounds other t h a n hydro- gen sulfide; the method is much more rapid, requiring for n determination instead of hours, from seven t o ten minutes, depending upon the purity of the gas.

The advantages of the volumetric cadmium chloride method over the Tutwiler are several. Twenty- eight times as much gas is used in the average de- termination as is used in the Tutwiler; t he burette readings are one-tenth those of the Tutwiler and much more accurate results on gas of low hydrogen sulfide content are obtained. A test can be made in from seven t o ten minutes.

Instead of a meter, a graduated cubic foot bottle may be employed for measuring the volume of gas used.

UNIVERSITY O F h4INXESO'TA ~ I I N N E A P O L I S

London Journal of Gas Lighting, 4, 3 / 1 0 , p. 41: 4, 1 2 . 10, p. 18.

A-VD E;VGI.VEERING C H E M I S T R Y VOI. j, SO. IO

A METHOD FOR THE DETERMINATION OF PHOS- PHORUS IN VANADIUM STEEL AND FERRO-

VANADIUM c'. F. S l D E N E R A N D P. hf . SKARTVTSDT

Keceived July 21, 1913

This paper embodies the adaptation of some well- known reactions t o the determination of phosphorus in vanadium steel and ferro-vanadium, together with results obtained by the method, which is as follows: The sample is dissolved in dilute nitric acid. If an insoluble metallic residue remains, a little hydro- chloric acid is also added. The solution thus obtained is evaporated t o dryness and baked until the nitrate of iron is decomposed. The residue is dissolved in concentrated hydrochloric acid and about 0 . 0 2 gram of aluminium in the form of aluminium chloride is added. The solution is nearly neutralized with ammonia, heated almost t o boiling, and the iron reduced by the gradual addition of a concentrated ammonium bisulfite solution with stirring. The re- duction is best accomplished by keeping the solution slightly acid until nearly reduced. and then adding ammonia until a slight permanent precipitate of iron hydroxide remains after vigorous stirring. finally dis- solving the precipitate with a few drops of ammonium bisulfite. To the solution, now smelling quite strongly of sulfur dioxide, one or two cc. of phenylhydrazine' are added drop by drop with stirring. If no precipitate appears, a few drops of ammonia are added until a slight permanent precipitate is formed. Then a few drops more of phenylhydrazine are added t o complete the precipitation. The solution is boiled about two minutes, allowed to settle and filtered.

This precipitate consists of aluminium phosphate, aluminium hydroxide and more or less of the vanadium. After washing with hot water until t he washings show no cloudiness when tested with mercuric chloride, the precipitate is dissolved off t he filter in to the original beaker with dilute nitric acid.

In the nitric acid solution containing the phosphorus and vanadium, the la t te r is oxidized b y the addition of a little hydrogen peroxide, and then a slight excess of sodium carbonate is added. T h e solution is boiled for about five minutes and t h e phosphorus precipitated as aluminium phosphate b y gradually adding dilute nitric acid until the solution no longer gives an im- mediate brown tinge t o turmeric paper.2 I t is im- por tan t t h a t this point be very carefully noted. The precipitate is filtered off and washed with a I per cent solution of ammonium nitrate. I t is then dissolved off the filter into an Erlenmeyer flask with dilute nitric acid and a little hydrogen peroxide added, which will produce a deep red color if much vanadium is present and a pinkish yellow if bu t a trace is present. If this test shows the presence of even a trace of vanadium, another precipitation with sodium carbonate and nitric acid is necessary. The number of precipitations required t o separate the phosphorus from the vanadium depends upon the amount of vanadium in the sample. For those containing up t o I per ren t , ii single pre- cipitation is sufficient; I t o j per cent, two precipita-

1 Hess and Campbell, J . Am. L ' k r m . Soc., 21, i76. ? C . M. Johnson, "Chemical Analysis of Special Steels," p. 26