chemical monitoring and management
DESCRIPTION
COMBUSTION. POLLUTANT. OZONE. AIR. PROTECTANT. CFCs. OTHER POLLUTANTS. CHEMICAL MONITORING AND MANAGEMENT. HABER PROCESS. WATER. IDENTIFYING IONS. HUMAN USE. WASTE WATER. AAS. SULFATE. CHEMICAL MONITORING AND MANAGEMENT. - PowerPoint PPT PresentationTRANSCRIPT
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CHEMICAL MONITORING
AND MANAGEMENT
AIR
OZONE
WATER
WASTE WATER
HUMAN USE
OTHER POLLUTANTS
POLLUTANT
PROTECTANT
CFCs
IDENTIFYING IONS
SULFATE AAS
COMBUSTION
HABER PROCESS
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CHEMICAL MONITORING AND MANAGEMENT
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SUBSECTION 1Much of the work of chemists involves
monitoring the reactants an products of reactions and managing reaction conditions
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Subsection 1 1.2.1 & 1.3.1
* specific chemical occupation named industry branch of chemistry e.g. analytical chemistry explain a chemical principle that the chemist
uses • GC/GLC – adsorption, solubility (text example)
1.2.2 collaboration between chemists – Text p. 198, 199
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1.2.3 monitoring combustion
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Subsection 2Chemical processes in industry
require monitoring and management to maximise
production
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NitrogenAmino Acids
R OH N C C O H H
Nucleic Acids
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THE HABER PROCESS
The reaction of N2 gas with H2 gas to form NH3 that eventually comes to EQUILIBRIUM in a CLOSED SYSTEM. Under normal conditions of T and P reaction proceeds very SLOWLY and the position of equilibrium is far to the LEFT.N2(g) + 3H2(g) 2NH3 H = -92kJ
bp -196oC bp -253oC bp -33oC
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THE HABER PROCESS
RAW MATERIALS* air nitrogen
Fractional distillation of air
* natural gas hydrogen From methane gas reacted with steam
CH4(g) + 2H2O(g) CO2(g) + 4H2(g)
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THE PRODUCTION OF AMMONIA
* manufacture of the reactant gases, N2, H2
* purification* compression
* catalytic reaction to form NH3
* recovery of the NH3
* recycling of unreacted N2 and H2
THE SIX MAIN STEPS
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THE HABER PROCESSThe conflict between rate and extent of
reaction (yield) – three key aspects need to be considered in choosing the conditions
* the yield – how far the reaction goes (how much NH3)
* the rate – how fast the ammonia is formed
* the energy account – how much energy can be saved/obtained
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THE HABER PROCESSThe compromise between
temperature, pressure and yield of ammonia within the extreme positions of:
* a high yield but low rate of reaction at low temperatures (e. g. 25oC)
* a low yield but high rate of reaction at high temperatures (1000oC)
* is achieved by using A CATALYST its role is to permit a reduction in the operating
temperature in the converter
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THE HABER PROCESS* Catalyst lowers the activation
energy so that the N2 bonds and H2 bonds can be more readily broken
* At these lower temperatures, the reduced Ea via the catalyst means more reactant molecules have sufficient energy to overcome the energy barrier to reacting (activation energy) so the reaction is faster
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YIELD OF AMMONIA* At each pass through the reactor, only
about 15% of the reactants are converted into products under these conditions, but this is done in a short time period.
* Ammonia is cooled and liquefied at the reaction pressure, & then removed as liquid ammonia.
* The remaining mix of nitrogen and hydrogen gases (85%) are recycled & fed in at the reactant stage.
* The process operates continuously & the overall conversion is about 98%.
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MONITORING OF HABER PROCESS
* incoming gas stream ratio H2:N2 of 3:1 pressure - too low and yield of NH3 drops, too high
shortens the life of the reaction vessel and unsafe – pressure sensors monitor
sensors monitor levels CO and CO2 as poison catalyst
CO(g) + H2O(g) CO2(g) + H2(g)
CO2(g) + H2O(l) + K2CO3(aq) 2KHCO3(aq) CO2 piped to urea plant where reacted with NH3 to form
urea (NH2CONH2) or sold to brewers and soft drink manufacturers
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MONITORING OF HABER PROCESS
* optimum temperature in converter temperature sensors monitor as too high damages
catalyst and reduces yield
* activity of catalyst particle size monitored to ensure high surface area
* purity of ammonia produced* energy use
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THE HABER PROCESS
2.3.1 gather and process information from secondary sources to describe the conditions under which Haber developed the industrial synthesis of ammonia and evaluate its significance at that time in world history case study
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THE HABER PROCESS* Fritz Haber, German chemist, 1868-
1934* winner of the Nobel Prize in Chemistry
(1918) for the synthesis of ammonia from
its elements* Carl Bosh developed the industrial
stages for the Haber process. The perfection of the Haber-Bosh process encouraged Germany to enter in World War I.
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Case Study
Demand for fertiliser* sources of fixed nitrogen
Chile saltpetre (NaNO3) exported to Europe in mid-19th century
coal-gas industry – ammoniacal liquor (NH3 in water) by-product processed to (NH4)2SO4
Explosives – nitroglycerineDyestuffs - 1856 start of synthetic
dyes – nitrogenous compounds20
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Case Study* all these demands could not be
satisfied by Chile saltpetre
* needed a process to fix atmospheric N2
* 1904-1908 Fritz Haber developed the process of synthesising NH3 from N2 and H2
high pressure, 450oC, catalyst
* Carl Bosch developed it as an industrial process - 30,000 tons by 1913
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Case StudyPolitical Unrest* Britain and allies controlled the sea-
routes for Chile saltpetre* Germany cut off from this source of
fixed N2
* WWI 1914 plant increased to 120,000 tons and a second plant up and running
* Germany increased munitions increased fertiliser for food production
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Case Study
Social consequences of Haber process
* prolonged WWI by 1-2 years – almost 1 million more deaths
* vast expansion of production of fixed N2 for fertilisers
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HTTP://WWW.YOUTUBE.COM/WATCH?V=C4BMMCUXMU8
HABER PROCESSHABER PROCESS
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3.2.1 deduce the ions present in a sample from
the results of tests
Cations – Ba2+, Ca2+, Pb2+, Cu2+, Fe2+, Fe3+
Anions - PO43-, SO4
2-, CO32-, Cl-
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3.3.2 gather, process and present information to describe and explain
evidence for the need to monitor levels of one of the above ions in
substances used in society
* Pb poisoning
* PO43- - eutrophication of
waterways leading to algae “blooms”
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Chemical Analysis
* Qualitative identify what species are present in a sample
e.g. vitamin tablet contains copper salt
* Quantitative determine the amount/concentration of
species present in a sample
e.g. vitamin tablet contains 1.2mg copper volumetric, gravimetric, instrument - AAS
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Identification of Ions1. A solution contains Cl- ions. Identify
an appropriate cation solution that could be added to detect the presence of these chloride ions.
2. A solution forms a white precipitate with carbonate ions and no precipitate with hydroxide ions. What common cation is most likely present in the solution?
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Identification of Ions
3. A solution forms a precipitate with a solution of sodium phosphate, no precipitate with sodium sulfate and no precipitate with sodium chromate. What is the identity of the cation?
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Identification of Ions
Risk Assessment
* moderately toxic – Ba cpds, AgNO3, (NH4)2MoO4 , CuSO4 , KSCN, NH3 solution
* highly toxic – Pb cpds waste collected in separate beaker – filter PbI2
* corrosive – 4M HNO3, 2M NaOH
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Identification of Ions
Hazard Minimisation* small quantities* fume cupboard for ammonia
solution, good ventilation* safety glasses (corrosive
solutions), lab coats* work near water supply and wash
hand at end
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Identification of CationsLead (II)
Pb2+(aq) + 2I-
(aq) PbI2(s)
(canary yellow ppte)Copper(II)Cu2+
(aq) + 2OH-(aq) Cu(OH)2(s)
(light blue ppte)Cu(OH)2(s) + 4NH3(aq) [Cu(NH3)4]2+
(aq)+ 2OH- (complex ion)
(royal blue solution)32
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Identification of Cations
Iron(II)Fe2+
(aq) + 2OH-(aq) Fe(OH)2(s)
(greenish ppte)
3Fe2+(aq) + 2[Fe(CN)6]3-
(aq) Fe3[Fe(CN)6]2(s)
(dark blue ppte)
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Identification of Cations
Iron(III)Fe3+
(aq) + 3OH-(aq) Fe(OH)3(s)
(brown ppte)Fe3+
(aq) + SCN-(aq) FeSCN2+
(aq)
(complex ion)
blood red
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Identification of Cations
CalciumCa2+
(aq) + CO32-
(aq) CaCO3(s)
(white ppte)
BariumBa2+
(aq) + CO32-
(aq) BaCO3(s)
(white ppte)
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Identification of AnionsCarbonate
CO32-
(aq) + 2H+(aq) CO2(g) + H2O(l)
pH of solution alkalineChloride
Cl-(aq) + Ag+(aq) AgCl(s)
(white precipitate)Sulfate
SO42-
(aq) + Ba2+(aq) BaSO4(s)
(white precipitate)
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Identification of Anions
Phosphate ammonium molybdate reagent
12(NH4)2MoO4 + PO43- + 3H+
(NH4)3PO4.12MoO3(s) + 12H2O + 21NH3
ammonium phosphomolybdate (yellow precipitate on heating)
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3.3.2 gather, process and present information to describe and explain evidence for the need to monitor levels of one of the above ions in substances used in society
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SPECTROSCOPY
white light
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SPECTROSCOPY* many substances can be heated to a point
at which they will emit electromagnetic radiation
* excitation of the atoms forces electrons to higher energy levels “excited state”
* movement of the electron to a lower energy level requires the loss of a specific amount of energy corresponding to that transition
* the excited atom can emit this energy as visible, IR or UV radiation
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Flame Test - Emission
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42n=1
n=2
n=3
n=4
Spectrum
UV
IR
Vi s ible
Ground State
Excited State
Excited StateExcited State unstable and drops back down
•Energy released as a photon
•Frequency proportional to energy drop
Excited State
But only as far as n = 2 this time
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Flame Emission
* electron normally in Ground State
* energy supplied [ as heat or electricity]
* electron jumps to higher energy level
* now in Excited State - UNSTABLE
* drops back to a lower level
* energy that was absorbed to make the
jump up is now released as a photon
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EMISSION SPECTRUM* each element has unique atoms so emits
an emission spectrum with a unique pattern of colours (wavelengths)
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EMISSION SPECTRA
H
Hg
Ne
Each element has a unique emission spectrum
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ABSORPTION SPECTRUM
* when an unexcited substance is exposed to a source of radiation containing the full range of wavelengths is will absorb specific characteristic wavelengths corresponding to the electron transitions to “excited” states
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ABSORPTION SPECTRUM
* if the light is analysed after it passes through the substance it will show gaps corresponding to the absorbed wavelengths forming an absorption spectrum
* Absorption Spectroscopy is the study of substances by analysing their absorption of specific wavelengths of radiation
H
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EMISSION AND ABSORPTION
Hydrogen emission spectrum
Hydrogen absorption spectrum
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SUBSECTION 3Manufactured products, including
food, drugs and household chemicals, are analysed to determine or ensure their chemical composition
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3.2.2describe the use of AAS in
detecting concentrations of metal ions in solutions and
assess its impact on scientific understanding of the effects of
trace elements
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USES OF AASTrace Elements* elements needed in small quantities for
proper functioning of plants and animals* e.g. Cu, Zn, Co, Mn* plants absorb minerals from the soil* animals get these minerals from the
plants* if soil is lacking in minerals –
humans/animals may show deficiency diseases
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USES OF AAS* sensitive analytical methods like AAS
led to the discovery of the role of trace elements in specific biochemical pathways
* soil analysis allows farmers to monitor levels of trace elements – treat problem
* blood and urine analysis can detect trace element deficiencies causing disease – change diet/give supplement
* SSB p. 51, 52
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USES OF AAS
* AAS far superior to “wet” methods like precipitations tests – slow, do not detect very low concentrations, not as specific (may precipitate more than one ion)
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3.3.5 gather, process and present information to interpret secondary data from AAS measurements and evaluate the effectiveness of this in pollution control
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USES OF AAS
Pollution Control* heavy metals include elements such as
Pb, Hg, Cd, Cr* Hg in water absorbed by some organisms
and concentrated in tissues* oysters/mussels (filter feeders) filter
polluted water and Hg/Cd/Pb concentrates in tissues
* other organisms feed off these and further concentrate heavy metals in their tissues
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USES OF AAS
* EPA requirements industrial wastewater diluted until [Hg] < 2ppm fish and shellfish contain Hg <= 0.5ppm
* AAS can be used to measure the level of Hg in seafood
* SSB p. 128 Heavy Metals
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SUBSECTION 5Human activity also impacts on
waterways. Chemical monitoring and management assists in providing safe water for human use and to
protect the habitats of other organisms
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5.2.1 Identify that water quality can be determined by considering
* concentration of common ions Cl-, OH-, HCO3
-, NO3-, SO4
2-, CO32-, PO4
3-
Na+, K+, Ca2+, Mg2+
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* total dissolved solids usually ionic salts
* hardness level of Ca2+ and Mg2+ ions
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5.2.1 Identify that water quality can be determined by considering
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* turbidity clarity of the water reflects level of suspended solids
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5.2.1 Identify that water quality can be determined by considering
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* acidity – measure the pH
* dissolved O2 (DO) high level of dissolved O2 supports a large
variety of aquatic organisms
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5.2.1 Identify that water quality can be determined by considering
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* biochemical O2 demand (BOD) measures how fast the O2 is being used up by
microorganisms may be measured over 5 days BOD5 = DO0 (mg/L) – DO5 (mg/L)
> 5mg/L indicates polluted water
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5.2.1 Identify that water quality can be determined by considering
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Biochemical Oxygen Demand BOD
* Biochemical Oxygen Demand is a measure of how much dissolved oxygen is being consumed as microbes break down organic matter.
* A high demand, therefore, can indicate that levels of dissolved oxygen are falling, with potentially dangerous implications for the river's biodiversity.
* High biochemical oxygen demand can be caused by: high levels of organic pollution, caused usually by poorly
treated wastewater; high nitrate levels, which trigger high plant growth.
* Both result in higher amounts of organic matter in the river. When this matter decays, the microbiological activity uses up the oxygen.
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Town Water Supply
* catchment area sources of contamination
* chemical tests turbidity, dissolved oxygen, pH, nitrate,
phosphate, conductivity/salinity, hardness other - bacteriological
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* physical processes sedimentation filtration – anthracite, sand, gravel
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Town Water Supply
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Town Water Supply
* chemical processes/additives alum/polyelectrolyte to flocculate clay particles chlorine – disinfection fluoride – dental protection lime (CaO) – raise pH to neutral as alum
acidifies water
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Filtration
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Membrane Filters
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AAS & Water Monitoring
ADVANTAGES* little sample preparation needed* each metal ion in a mixture of ions can be
determined * high sensitivity – detects ppm or ppb- ideal
for use in water quality analysis* cost effective compared to more labour
intensive techniques like titrations, precipitations
* fast, automated technique so can measure large number of samples quickly
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AAS & Water Monitoring
* disadvantage – does not measure biological measures of water quality dissolved oxygen BOD bacterial contamination
POTABLE water is water of sufficiently high quality that it can be consumed or used with low risk of immediate or long term harm.
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5.3.2 Eutrophication of Water
* the enrichment of a water body with nutrients such as nitrate and phosphate
* increases the possibility of algal blooms* main sources of phosphate
sewage – decomposition of organic matter, detergents fertiliser runoff
* effects – text p. 286, SSB p. 125-127* monitoring – text p. 288, SSB p. 139
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5.3.2 Eutrophication of Water
* Phosphates used as builders in detergents – complex with calcium and magnesium ions (hard water)
* Calcium and magnesium ions can cause small colloidal particles like clay to flocculate which soils clothes in the wash.
* Builders give detergents better cleaning power.
* Sodium zeolite is now being used to replace phosphates in detergents
* Zeolites are complex compounds containing metal ions bound to an aluminosilicate lattice – calcium and magnesium ions are exchanged for sodium ions so softens the water
* Zeolites cannot cause the eutrophication problems associated with phosphates
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5.3.2 Eutrophication of Water
* Algal bloom likely [phosphate] > 0.05 ppm dam/lake [phosphate] > 0.1 ppm river/stream (higher
value as likely to be flowing)
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5.3.2 Eutrophication of Water
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2010 Water Quality - Wonga
Parameter Excellent House Lagoon
Bagnell’s Lagoon
Tank
pH 6.0-7.5 6.5 6.5 5.2
TurbidityNTU
< 15 13 26 <10
SalinityS/cm
< 100 465 112 20
TemperatureoC
11.4 11.6 11.4
Oxygen Sat.%
80-90 37 55 91
Hardness (ppm)
< 75 19 40 0
NO3- (mg/L) < 0.05 below
detectable level
below detectable
level
0.88
PO43- (mg/L) < 0.01 below
detectable level
6 20
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2011 Water Quality - Wonga
Parameter Rating Black
Lagoon
Bagnell’s Lagoon
Tank
Temperature
(oC)
Poor
0-5
Good
5-20
Poor
20-30
8.8 13 9
pH Poor
<6
Healthy
6-8
Poor
>8
5 6 5
Conductivity
(uS/cm)
Healthy
<300
Fair
300-800
Poor
>800
110 520 10
Turbidity
(NTU)
Healthy
<10
Fair
15-30
Poor
>30
29 17.5 <10
Phosphates
(ppm)
Good
0-5
Fair
5-15
Poor
15-30
5 5 4
Nitrites
(ppm)
Good
<0.1
Fair
<0.2
Poor
<0.4
0.2 0.1 <0.15
Hardness
(ppm)
Soft
0-50
Hard
120
Very hard
250-425
50 120 0
Oxygen Saturation
(%)
Poor
<80
Good 80-90Healthy waterways need O2 level > 6mg/L
High quality fresh water 9mg/L
40 25 51
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Destructive/Non-destructive Testing
Determination of Dissolved Solids
* Using a conductivity meter measures the conductivity
(concentration of ions) in the sample does not change the sample so it can
be used for further testing e.g. pH
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Destructive/Non-destructive Testing
* Filtration and evaporation procedure destroys sample some salt left in filter paper spitting of salt when heating potentially lower result soot on evaporating basin if not always blue
flame may potentially give a higher result
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