HAND BOOK ON

WATER TESTING

Chief Editor Dr. R.N. Ray, Ph. D (I.I.Sc., Bangalore)

Editorial Board Mr. Utkal Ranjan Mohanty

Dr. Sashikanta Dash Mr. Satyabrata Swain

Publisher & copy write BHARAT JAN GYAN VIGYAN SAMITI ( BJGVS) N-3/309, IRC Village,

Bhubaneswar 751015 Tel Ph. (0674) 6532523

Printed by Milan Enterprises, Jaydev Vihar, Bhubaneswar.

CONTENT SL.NO. SUBJECT PAGE 1. INTRODUCTION 3 2. ABOUT THE COMPONENTS 6 3. GUILDELINES TO COLLECT SAMPLES 11 4. WATER ANALISIS 14 5. CHEMICAL TESTS MEASUREMENT OF PH OF WATER 19 6. TEST OF TOTAL SOILDS IN WATER 21 7. TEST OF ALKALINITY OF WATER 23 8. TEST OF HYRDNESS OF WATER 25 9. TEST OF ACIDITY* OF WATER 29 10. TEST OF CHLORIDE 31 11. TEST OF DISSOLVED OXYGEN (DO) 34 12. TEST OF BIOCHEMICAL OXYGEN DEMAND (BOD) 38 13. TEST OF IRON IN WATER 40 14. TEST OF FLUORIDE IN WATER 43 15. TEST OF ARSENIC IN WATER 47 16. TEST OF NITRATE IN WATER 49 17. TEST OF LEAD IN WATER 50 18. COLLECTION OF SOIL SAMPLE 52 19. ELECTRICAL CONDUCTIVITY OF SOIL 55

*** INTRODUCTION

Water & soil are most important natural resources as the quality of other resources depends directly or indirectly on the state of the surrounding soil and eater. The unique properties of water allow it to play a major role in shaping the landscape and in creating special habitats both Animals and plants. Most of man's activities centre around water. Civilisation flourishes only in those areas where there is a sufficient and regular supply of water of animal life, too is dependant on the availability of this precious resource. Agriculture and industrial activities also need a constant and regular supply of water like air and water, soil is an important component of our environment. It plays a pivotal role in the growth of life and in the maintenance of ecosystem. Soil has been defined as the thin layer of the earth's crust on which biological activities take place. Soil provides a base for plants to stand or and also provides the necessary nutrients to plant. But due to rapid industrialization, indiscriminate use of harmful chemicals and mindless behaviour of human being have made the water and soil around us polluted, when often makes them unfit for human consumption and agriculture use. It is, therefore, necessary that we have a working knowledge about water and soil in very perfect manner. It is equally important for us to realize the effect our actions have on two precious resources. This handbook along with the kit chiefly aims at providing ways to monitor the quality of potable water and stand and siol. The various analysis listed here i.e. physical, chemical and biological tests listed here for both the resources are simple are simple, cost effective, easy to perform and have been standardized and tested for reproducibility. The methods outlined here are for relative quality testing. However for more accurate results it is advised to refer to other research labouratories for this purpose. It is expected that the hand book as well as the kit will be beneficial to farmers, school, and science communicators in testing and analyising water and soil quality especially in rural areas. SI Apparatus Required 1. 2. 3. 4. 5. 6. 7.

Beakers 2 Dropping bottles 25 Filter paper Measuring cyclinder 1 Microspatulas 8 Pasteur Pipettes 6 PH colour chart with PH paper

8. 9. 10. 11. 12. 13. 14. 15. 16.

Plaster Bottle (500 cm3) for sample collection 6 Plaster funnel 1 Polythene sample vial 1 Reaction plate 1 Spirit lamp 1 Narrow necked plaster bottle (125 cm3) 6 Thermometer 1 Triper stand 1 Wire gauze - 1

SI. No. Chemicals

1. 2. 3. 4. 5. 6. 7. 8. 9.

10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24.

1, 10-phenanthroline Alizarin red s / Spands Ammonia Ammonium ferrous sulphate Deionised water EDTA (Etlrylene Tetra Acitic Acid) Eriochrome Black T Ethanol Hydrochloric acid Hydroxylamine hydrochloride Iodine Manganous sulphate Phenolphthalein Potassium chromate Potassium iodide Silver nitrate Sodium arsenite Sodium fluoride Sodium hydrogen carbonate (Baking Soda) Sodium hydroxide Sodium thiosulphate Starch Sulphuric acid Zirconium oxy chloride

ABOUT THE COMPONENTS

I. The Reaction Plate

This plate forms a series of well of same size, which can be considered as micro test tube. There are four wells in a column and six such columns. The wells are identified by numbers in column and alphabet in rows. For example the well A1 indicates that it is the first well in the row A and the well C3 indicates that it is the third well in the third row, namely row C.

Merits:

i) The reaction plate is made of durable, non-wettable polystyrene, making it easy to clean.

ii) It can be mildly heated or colled by floating the entire reaction plate in a suitably large container filled with warm or cold water. Alternately, the container filled with warm or cold water. Alternately, the contents of a particular well may be heated by inserting a heated glass rod into that well.

iii) It is generally resistant to dilute acids, bases, aqueous solutions of salts, saturated hydrocarbons, oils, greases, fats and most alcohols.

Demerits : (Caution!)

i) The reaction plate should not be heated with an open flame nor brought into contact with a direct source of heat, as it will cause the plate to melt.

ii) The reaction plate is not resistant to concentrated inorganic acids (except hydrochloric acid), aromatic and chlorinated hydrocarbons, esters and ketones, tetrahydrofuran and dimethylformamide.

If you are uncertain if a particular chemical, which is not listen above, can be used is the reaction plate, add some of this chemical to one of the small wells as a test. If, after few minutes, the well looks like as if being dissolved or getting discoloured then that chemical is not suitable for the reaction plate.

A. How to clean the wells in the reaction plate :

The wells can be cleaned in a number of ways:

a) Hold the well under running tap water. This rinses the wells of whatever was in them.

b) Place the wells in a container with tap water. (The water should be sufficient to cover the wells). Allow the wells to soak until clean.

c) If a precipitate has settled into a well, roll up a piece of tissue paper, wet it, then push it into the well. Turn the "well cleaner" around in the well several times until the precipitate has been wiped off completely.

d) If the well is still stained after following the above procedures, use a plastic pipette to add a sufficient number of drops of hydrochloric acid (11 M) to the affected well.

e) Covering the stain. (Do not soak the well for a prolonged period of time with acid, this may further stain the well. Once loosened, repeat step c as above)

It is strongly advised to clean the wells of the reaction plate as soon as possible after use. This will minimize chances for deterioration of the plastic.

B. How to dry the wells in a reaction plate:

The wells can be dried in a number of ways :

a) Shake the reaction plate until all the drops in the well have come out.

b) Roll up a piece of dry tissue paper and push it into each well until all the wells are dry.

Other applications of the reaction plate :

1. The reaction plate may be placed on the overhead projector and used to project the experiment in progress.

2. If the underside of the reaction plate is filled with water and frozen, then it can be used as a refrigerated plate where necessary.

II. Pasteur Pipettes (6 Nos.) :

The Pasteur are not-wetting and can be easily cleaned by rinsing with water and hence are reusable. They have a maximum capacity of 2 cm3. Two of the Pasteur pipettes are graduated.

Merits :

a) Pipette can be used to store, transport and dispense solutions like dilute acids and bases and aqueous solutions of salt.

b) They can be mildly heated by immersing the bulb of the contents in warm water.

Demerits :

a) Pipette cannot be heated with a direct flame, because it will melt.

b) Organic solvents (such as acetone, hexane) and corrosive chemicals (such as conc. sulphuric acid) cannot be stored in the pipette.

III. Measuring Cylinder:

It is a plastic measuring cylinder which can be used to measure the volume of the liquid. The maximum capacity that can be measured is 10 cm3. It is resistant to dilute acids, bases and salt solutions. But the measuring cylinder cannot be used to measure organic solvents.

IV. Spirit Lamp :

The spirit lamp is a metal container with a screw type bras holder through whih the wick passes, methylated spirit, rectified spirit is used as fuel. It is stable and unbreakable. The metal cover is used to extinguish the flame.

V. Dropping Bottle :

The dropping bottles provided in the kit can be used to store liquids (dilute acids and bases and aqueous salt solutions). They can be mildly heated by immersing in warm water. They are non-wettable. They are ideal to dispense solutions in drops into the reaction plate.

VI. Beakers :

A glass beaker and unbreakable plastic beaker are provided in the kit. The glass beaker can be used for storing any (organic or inorganic) solid or liquid. The plastic beaker is used to store dilute acids and bases and aqueous salt solutions.

VII. Thermometer :

An alcohol thermometer with a cover is provided with the kit. The maximum temperature that can be read with the thermometer is 50o C.

Caution : Do not drop the thermometer on to a hard surface. It is breakable.

For 'Do' Measurements

VIII Polythene Vial

IX. Stoppered plastic bottle (100cm3)

Other items in the kit

X. Funnel

XI. Filter Paper

XII. pH paper

XIII. pH Colour chart

XIV. Sample Bottles to ollect water

XV. Microspatulas

XVI. Plastic Box.

PARAMETERS FOR WATER QUALITY

CHARACTERIZATION AND STANDARDS FOR POTABLE WATER

SI. NO.

Observation Tolerance Standard

1. Appearance -- Free from any insoluble matter

2. Colour 5 units on the Pt-Co Colourless

scale 3. Odour Unobjectionable Colourless 4. Taste Unobjectionable Tasteless 5. pH value 6.7-7.9 6.0-8.5 6. Specific conductance -- 300 Nmho cm-1 7. Hardness Less than 200 ppm as

Ca CO3 100-150 ppm CaCO3

8. Nitrite nitrogen ---

cup. (The glass or metal cup etc. should never be used for this purpose). It should be rinsed out at least three times with the water that is to be sampled before it is filled.

3. Sampling site can be chosen before and after any sources of pollution

4. Samples must be collected from slow running and undisturbed water streams.

5. The best way to collect sample from stream is to tie a bottle to the end of a long stick and collect the sample as far away from the blanks as possible.

6. Samples must be collected midway across the river and midway between the top and bottom of the river.

7. Sampling sites can be chosen as many as desired to get and even picture of water quality of the river.

8. At the site of sampling, record

a) time and date of sampling

b) name of the site (a number can be given)

c) any nearby source of pollution or activities which can cause change in water quality.

d) Vegetation on the banks (trees, plants, grass etc.)

e) animals

f) the nature of soil surface (rocky, muddy, clay etc.)

g) colour and odour of water and temperature.

9. Certain examinations should be carried out at the time the sample is collected : these include temperature, pH and residual chlorine, for example. The estimation of free carbon dioxide should also be carried out at the time the sample is collected, but if this is not practicable a special sample should be collected for this purpose; the bottle should be filled completely and the sample kept cool with ice until it is examined.

10. A special sample is also required for the dissolved oxygen test. The sample should be collected in a narrow-necked bottle of 125 cm3 capacity having an accurately fitting glass or polythene stopper. If the sample is collected from a tap, the water should be passed down a glass tube to the bottom of the bottle and allowed to overflow for 2-3 minutes before the stopper is inserted. When samples are taken from a stream or reservoir a suitable apparatus, to ensure that the water in the sampling bottle is displaced several times, should be used. The dissolved oxygen in the sample should be "fixed" on the spot

as soon as the sample has been collected. The water temperature at the time of sampling should be recorded in degrees Celsius.

11. For certain constituents the immediate analysis is required because the composition of water may change before it comes to the laboratory.

The maximum limits of storage are :

i) Highly polluted waters 10-12 hous

ii) Slightly polluted waters 48 hours

ii) Unpolluted water 80 hours

Sometimes the change in temperature also changes the pH value as the dissolved gases (O2, CO2, H2, S) may be lost.

DONT'S

1. Samples should not be collected from a site very close to the banks of the river.

2. Samples should not be collected from stagnant or shallow water.

3. There should not be any disturbance near the site of sample collection, like people bathing or pipes discharging effluents etc.

TYPES OF ANALYSIS

1. Physical i) Colour ii) Odour iii) Taste iv) Turbidity v) Temperature 2. Chemical i) pH ii) Total solids iii) Alkalinity iv) Hardness v) Acidity

vi) Chlorides vii) Dissolved oxygen, (DO) viii) Bio chemical oxygen demand (B.O.D.) ix) Iron x) Fluoride xi) Arsenic xii) Nitrate xiii) Lead 3. Biological :

WATER ANALISIS PHYSICAL TEST Introduction 1) Colour : The potable water (drinking water) has no colour i.e. colourless. By colour it

means those hues inherent with in water itself, which have arisen due to the presence of colloidal substances and materials in solution. In natural water coloas are imparted by metallor ions, suspended matter, industrial effluents etc.

Material needed :

Apparatus Reagents Beaker A white piece of paper

Water sample

Procedure and observation Take the water sample in a transparent container i.e. beaker and plate a piece of white

paper below the beaker. Then observe the colour and record. Result : The colour of the water sample is ___________ 2) ODOUR : Introduction : The odour of the potable (drinking water) has no specific odour i.e. odourles. Due to the

presence of impurities, water sample has any odour especially simillare to cooking gas, chlorinous, fishy, mouldy, earthy, rotten eggs or aromatiz odour.

Material needed :

Apparatus

Reagents

Polythene sample vial Water sample

Take a sample vial and fill it 2/3, with water sample and shake it for 5 minutes. Note if

frothing is produced which generally suggests the presence of impurities. Find out the odour and record our observations. Result : The odour of the water sample is ___________________. 3) TASTE : Introduction : The taste of the potable water has no taste i.e. tasteless. The taste of the

water also varies with the colour. The odourless water has a distinct taste. Material needed :

Apparatus Reagents Polythene sample Vial

Water sample

Take a sample vial and fill it 2/3, with water sample and shake well for 5 minutes.

- By tasting the sample and record your observations. Result : The taste of the water sample is _______________ 4) TURBIDITY : Introduction

The turbidity is a measure of water clarity. The material suspended in water decreases the passage of light through the water. Suspended materials includes soil particles (clay, silt, and sand), algae, plankton, microbes, and other substances. These materials are typically in the size range of 0.004 mm (clay) to 1.0mm (sand). Turbidity can affect the color of

the water. Higher turbidity increase water temperatures because suspended particles absorb more heat. This, in turn, reduces the concentration of dissolved oxygen (DO) because warm water holds less DO than cold. Higher turbidity also reduces the amount of light penetrating the water, which reduces photosynthesis and the production of DO. Suspended materials can clog fish gills, reducing resistance to disease in fish, lowering growth rates, and affecting egg and larval development.

Sources of turbidity include:

- Soil erosion - Waste discharge - Urban runoff - Eroding stream banks - Large numbers of bottom feeders (such as carp), which stir up bottom sediments - Excessive algae growth.

Materials needed

Apparatus Reagents Sampling bottle White paper* Marker pen* Measuring cylinder (Glass)

Water samples

Not provided with the kit

Sampling techniques : 1. Collect the sample in a bottle or bucket in mid-stream and mid-depth if possible. Avoid

stagnant water. The sample as far from the shoreline as possible is best. Avoid collecting sediment from the bottom of the stream.

2. Face upstream as you fill the bottle or bucket. 3. Carefully stir or swish the water in the bottle or bucket until it is homogeneous, taking

care not to produce air bubbles (these will scatter light and affect the measurement). Produce : 1. Mark any symbol on a white paper with a black marker pen. 2. Place the measuring cylinder on top of the symbol. Then pour 10cm3 of the collected

water slowly into the measuring cylinder while looking down the measuring cylinder.

3. Stop the addition of water when the symbol is just beginning to blur. 4. Measure the depth of the water column in the measuring cylinder when the symbol is not

seen clearly. (It is advised to use 10cm3 of good quality water first and check the clarity of the symbol at a depth of 10cm3).

Depth of water when the symbol is just not clearly visible

Turbidity

10 cm3 Clear 9 cm3 Slightly turbid 8 cm3 Turbid 7 cm3 Not potable

5. TEMPERATURE : Introduction : The rates of biological and chemical processes dependent on certain temperature ranges for their optimal health. Optimal temperatures for fish depend on the species : some survive best in colder water, whereas others prefer warmer water. Benthic macrovertebrates are also sensitive to temperature. If temperatures are outside this optimal ranges for a prolonged period of time, organisms are stressed and can die. Temperature is measured in degrees Fahrenhet (F) or degrees Celsius (C), For fish, there are two kinds of limiting temperatures; the maximum temperature that varies according to the time of year and the life cyle stage of the fist species. Reproduction stages (spawning and embryo development) are the most sensitive stages. Temberature affects the oxygen content of the water (oxygen levels become lower as temperature increases); the rate of photosynthesis by aquatic plants; the metabolic rates and aquatic organisms; and the sensitivity of organisms to toxic wastes, parasites, and diseases. Aquatic plants show an increase in growth with temperature rise while plant respiration and decay also increase thereby using up the limited oxygen available. Direct sunlight, removal of shading stream bank vegetation and human impact like dumping of wastes which absorb sunlight and water used for colling purpose when released into water bodies, increase water temperature by 4 to 50 C. Other causes of temperature change include weather, impoundments (a body of water confined by a barrier, such as a dam), urban storm water, and groundwater inflows to the stream. Note : Temperature measurement of the water sample must be made at the site of collection to get accurate results.

**********

CHEMICAL TESTS MEASUREMENT OF pH OF WATER

Introduction : The pH scale serves a measure of acidity or alkalinity of water. It is logarithmic scale and varies from 0 to 14. 0 7 14

Acidic neutral Alkaline (basic) Acidic solutions have pH between 0 and 7 and alkaline solutions between 7 and 14. Pure water is considered neutral (neither acidic nor basic) with a pH = 7. pH of water is a critical component of biological systems. River water pH varies between 6.5 and 8.5 depending upon the salts dissolved in it. However addition of sewage, industrial waste and agricultural run-off ofter change the pH drastically, which affect aquatic life and destroy them. Hence measurement of pH is an important part of monitoring the water quality. Principal : Standard pH paper displays different colours in acidic and basic mediums. Material needed

Apparatus Reagents Non bleeding pH paper (range 2.0 - 10.5) Reaction plate Pasteur pipettes pH colour chart

Water sample Lemon Juice or vinegar Strong soap solution

# Optional Note : 1. Collect the sample in a polythene bottle. 2. Measure pH within 0-4 hours of collection. Procedure and observations : 1. Dispense 20 drops of water sample in well A1. 2. Take a leaf of the pH paper booklet and dip it is well A1. Note the coloure of the paper. 3. Compare the colour with the pH colour chart and note the pH reading in the field data

sheet. 4. Dispense 20 drops of lemon juice or vinegar in well A2. 5. Take a leaf of pH paper, dip it in well A2 and note that the colour changes to dark red

indicating it to be acidic. 6. Dispense 20 drops of strong soap solution in well A3.

7. Take a leaf of pH paper, dip it in well A3 and note that the colour changes to blue indicating that the solution is alkaline.

Result : The pH of the water sample is

********

TEST OF TOTAL SOLIDS IN WATER Introduction : Excess of dissolved solids decreases the palatability of drinking water and may cause gastrointestinal irritation. While desirable limit of dissolved solids is 500mg/dm3, a maximum limit of 1500 mg/dm3 is considered harmless. The total solids include water soluble as well as insoluble matter. Materials needed :

Apparatus Reagents Glass Beaker Plastic beaker Spirit lamp Funnel Filter paper * Dessicator * Filtration Stand * Weighing Balance Measuring cylinder

Water samples

* Boiling chips

* Not provided with the kit Total solids : Procedure : 1. Weight the glass beaker with a boiling chip (W1g). 2. Take 50cm3 of the filtered water into the glass beaker (use measuring cylinder for

measuring the volume). 3. evaporate the water carefully until the glass beaker becomes dry. 4. Cool in a dessicator and weigh the glass beaker along with the boiling chip to get

concordant value (W2g). Calculations : Weight of residue in mg (W2 - W1) Total solids ppm = ------------------------ X 100 Volume of sample Taken in cm3

Filterable residue : Procedure : 1. Weigh the glass beaker with a boiling chip (W 1g).

2. Filter the water sample into a plastic beaker using funnel, filter paper and filtration stand.

3. Take 50cm3 of the filtered water into the glass beaker (use measuring cylinder for

measuring the volume). 4. Evaporate the water carefully until the glass beaker becomes dry. 5. Coll in a dessicator and weigh the glass beaker along with the boiling chip to get

concordant value (W 2g). Weight of residue In mg (W2 - W1) Filterable residue in ppm = -------------------------- X 1000 Volume of sample Taken in cm3 Non-filterable residue in ppm = Total solids filterable residue Note : If water spurts, it is necessary to use a watch glass to cover the beaker.

TEST OF ALKALINITY OF WATER Introduction : Alkalinity of water may be defined as its capacity to neutralize acid. In natural water alkalinity is chiefly due to the presence of salts of weak acid and strong base (bicarbonates, carbonates and hydroxides etc.) Excessive alkalinity increases algae productivity and renders the water unpleasant to taste and unsuitable for irrigation . Principle : The alkalinity can be easily determined by titration with standard solution of strong acid using suitable indicator. In this experiment the sample of water is titrated with

standard hydrochloric acid using phenolphthalein as indicator. Phenolphthalein alkalinity measures the CO32- +OH content. The carbonate-hydroxide concentration is estimated by the amount of strong acid (moles/dm3) required to lower the pH of the sample of pH = 8.3). Materials needed

Apparatus Reagents Reaction plate Calibrated Pasteur Pipettes Microspatulas

Hydrochloric acid (0.1M)

Phenolphthalein Water Sample

Note : Use different pipettes for different solutions. Preparation of reagent :

1. Hydrochloric acid : Prepare 0.1M hydrochloric acid solution by diluting 0.83cm3 of concentrated hydrochloric acid (12M) to 100cm3 with distilled water.

2. Phenolphthalein indicator : Dissolve 0.5g of phenolphthalein in 50cm3 of 95%

ethanol. Dilute with 50cm3 of water. Procedure and observations :

1. Dispense 17 drops of water sample into well A1 of a clean dry reaction plate using calibrated pasteur pipette.

2. Add 1 drop of phenolphthalein indicator into the same well. 3. Add hydrochloric acid solution drop wise (counting the drops) using a calibrated

Pasteur pipette till the colure of the solution changes from pink to colourless. Note down the number of drops.

4. Convert the number of drops into volume as follows and enter in table 4.1. (Volume in cm3 = Number x drop value of the Pasteur pipette used). 5. Repeat the experiment for concordant values.

Table 4.1

Trial number Value of water Sample (cm3)

Volume of HCL (cm3)

1 2 3

Calculations : Volume of hydrochloric acid = VA cm3 Molarity of hydrochloric acid = MA = 0.1M Volume of water sample = Vs cm3 Phenolphthalein alkalinity (mg/dm3 of 1/2 co32- + OH-) = VA . MA 3 --------------x50x103 VS Result : The alkalinity of the water is estimated to be_______________ Note : After addition of indicator, if the solution remains colour less then Phenolphthalein alkalinity = 0.

TEST OF HYDRNESS OF WATER Introduction : Natural water is slightly acidic because of carbon dioxide dissolved in it to be form carbonic acid (H2CO3). When it flows over limestone (CaCO3) it dissolves CaCO3 converting it to soluble calcium bicarbonate and renders the water hard. CaCO3(S)+H2CO3 (aq) Ca2++2HCO3- (aq) (1) The use of hard water for domestic purposes and in industry presents several problems. For example soap consists of the sodium salts of long-chain carboxylic acids such as sodium

stearate (C17H35COO-Na+). In hard water, soap a scum of insoluble calcium salts of the long chain carboxylic acids, which has no cleaning power. When hard water is heated the bicarbonate decomposes to release carbon dioxide and calcium carbonate precipitates. (reverse of reaction 1). This calcium carbonate is the 'scale' that forms inside tea-kettles and in hot water pipes and boilers. Eventually, scale deposits may block a pipe completely. Temporary hardness is due to the presence of bicarbonate of Ca++ and MG++ while permanent hardness is due to suphates and chlorides of Mg++ and Ca++. In general term, hardness of water is due to the salts of calcium, magnesium, strontium, iron and manganese. The following cations and anions are responsible for the hardness of water. Cations Anions Mg++ HCO3------- Ca++ SO42------- Sr++ C1----- Fe++ NO3------ Mn++ SiO32----- When these ions are not present then the water is said to be soft. The hardness of water is not a pollution parameter but indicates water quality, mainly in terms of Ca2+ and Mg2+, expressed as CaCO3. Principal : Hardness of water is measured by complexometric titration using EDTA as the chelating agent and Eriochrome Black-T as the indicator. During the titration with EDTA (Na2h2Y), Ca2+ first reacts to form relatively stable CaY2-, followed by Mg2+ to give MgY2- complex, which is less stable). Excess EDTA finally reacts with Mg-EBT complex (indicator/wine-red) releasing the free indicator (blue). the colour changes from wine-red to blue at the end point. Ca2+ + H2Y2__ CaY2__ + 2H+ Mg + H2Y2___ Mgy___2 + 2H+ Mg----D___ + H2Y2 MgY2_ + HD___ + H+ (red) (blue) Materials needed

Apparatus Reagents Reaction plate EDTA solution

Calibrated Pasteur Pipettes Microspatulas

Eriochrome Black T solution Buffer solution Water samples

Preparation of the reagents : 1. EDTA solution (0.01M) : Dissolve 3.723g of disodium salt of EDTA in distilled water

and make up the solution of 1dm3. Store in polythene bottle. 2. Buffer solution : Add 142 cm3 of liquor ammonia (sp. gr. 0.88-0.90) to 17.5g ammonium

chloride (A.R. grade). Dilute to 250cm3 with distilled water. 3. Eriochrome Black T solution : Dissolve 0.4g of pure dyestuff in 100cm3 of ethanol. Note : Use different Pasteur pipettes for different solutions. Procedure and Observations : 1. Wash the reaction plate with distilled water. Dry the wells thoroughly. 2. Dispense 17 drops of water sample in well D1, using a calibrated Pasteur pipette. 3. Dispense 2 drops of buffer solution into the same well. 4. Dispense one drop of Erichrome Black T indicator into the well. Note that the colour

changes to wine red. 5. Stir the solution with a microspatula. 6. Now add EDTA in drops (use a calibrated Pasteur pipette and count the drops while

adding) till the colour changes to blue. (If necessary, stir the solution with a micro spatula).

7. Note down the number of drops and convert the number of drops into volume (in cm3) as

follows and enter in table 5.1. 8. Repeat the experiment to get concordant values. Table 5.1

Trial Number

Volume of water Sample (cm3)

Volume of EDTA (cm3)

1 2 3

Calculations : Volume of EDTA = V EDTA Molarity of EDTA = M EDTA = 0.01M Volume of water = V SAMPLE Hardness (mg/dm3 of CaCO3) in the sample = VEDTA x MEDTA x 105 ------------------------ VSAMPLE Note : 1cm3 0.01M EDTA = 1.0mg CaCO3 Result : Hardness of water sample has been estimated to be _______

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TEST OF ACIDITY* OF WATER Introduction : Sometimes the water shows acidity due to the presence of uncombined CO2 salts acids and weak bases and mineral acids. Excess acidity has adverse effects on aquatic life.

Principal : In order to determine the acidity of water, it is titrated with standard solution of a strong base by using a suitable indicator. Materials needed

Apparatus Reagents Reaction plate Calibrated pasteur pipettes Microspatulas

Sodium hydroxide (0.0IN) Phenolphthalein Distilled water Water Sample

Note : Use different pipettes for different solutions. Preparation of reagent : Sodium hydroxide (0.01N) : Dissolve 40mg of sodium hydroxide in 100 cm3 of water and standardize it by titrating with standard solution of oxalic acid with phenolphthalein as indicator. * Many water samples contain no titrable acid. Procedure and Observations : 1. Dispense 17 drops of water sample into well C1 of a clean dry reaction plate using

calibrated Pasteur pipette. 2. Add 1 drop of phenolphthalein indicator to the well using a Pasteur pipette. 3. Add sodium hydroxide solution dropwise (counting the drops) using a calibrated Pasteur

pipette till the colour of the solution changes from colourless to pink. Note down the number of drops.

4. Convert the number of drops into volume as follows and enter in table 6.1. 5. Repeat steps 1 to 4 for concordant values. Table 6.1

Trial Number

Volume of water Sample (cm3)

Volume of EDTA (cm3)

1 2

3

Calculations : Volume of sodium hydroxide = VB cm3 Molarity of sodium hydroxide = MB = 0.01M Volume of water sample = Vs cm3 Total acidity (mg/dm3 of CaCO3) = .

100 103

Result : The acidity of the water is estimated to be _____________

TEST OF CHLORIDE

Introduction : Chloride ion is generally present in natural waters due to dissolution of salt deposits. Hence the water with more of chloride is salty to taste but the same is not harmful till level is very high. For public health, chlorides upto 250mg/litre (ppm) are not harmful but increase of chloride beyond this are indication of organic pollution.

Human excrete and industrial wastes due to effluents from chemical industries and irrigation drainage are rich in chlorides. When the concentration is above 1000 mg per dm3, it harms agricultural plants and metallic pipes. A high chloride content indicates pollution of water with public sewage.

Principle : Chloride ion concentration is determined by titration with standard

silver nitrate solution. Potassium chromate is used as indicator in neutral or slightly alkaline solution. During titration, silver chloride precipitates out. When all the chloride ions have been precipitated as silver chloride, the excess silver nitrate reacts with potassium chromate to give orange-red silver chromate indicating the end point.

C1----- + Ag+ AgC1;

Ag+ + CrO22---- AgCrO4 ( excess )

Materials needed

Apparatus Reagents Reaction plate Calibrated Pasteur pipettes Microspatulas

Potassium chromate indicator * Deionised water Silver nitrate solution NaOH solution or dil. H2SO4 Non-bleeding pH paper Water Sample

* Not provided with the kit. Preparation of reagents : 1. Potassium chromate indicator : Dissolve 5gm of potassium chromate in 10 cm3 of

deionised water. 2. Standard silver nitrate solution (0.028N) : Dissolve 4.762gm of silver nitrate in

deionised water and dilute to 1000 cm3. Store in brown bottle. Note : a) All the apparatus should be thoroughly dried before starting the experiment. b) Different Pasteur pipettes should be used for different solutions. Procedure and Observations :

1. Dispense 17 drops of water sample in well A1 using a calibrated pipette.

2. Adjust the pH of the solution to 7-10 by adding 1 drop of NaOH or H2SO4. 3. Add 1 drop of potassium chromate indicator solution.

4. Add silver nitrate solution drop by drop while counting the number of drops (use a calibrated pipette).

5. Continue the addition of silver nitrate solution with intermittent stirring with a

microspatula till the solution turns permanent reddish tinge. (The red orange precipitate of silver chromate AgCrO4 starts precipitating).

6. Note down the number of drops of silver nitrate and calculate the corresponding

volume as follows and enter in the table 7.1. Volume in cm3 = No. of drops x drop value of pipette used. 7. Repeat steps 1 to 6 to get concordant values. Table 7.1

Trial number

Volume of water sample (cm3)

Volume of EDTA (cm3)

1 2 3

Calculations : Volume of silver nitrate used = V1cm3 Normality of silver nitrate used = N1cm3 Volume of water used = V2cm3 Amount chloride ion (mg/dm3) of the sample = X.

(Alternately, 1cm3 of 0.0282N AgNO3= 1mgC1) Result : Amount of chloride in the water sample is ____________

**********

TEST OF DISSOLVED OXYGEN (DO) Introduction : Living organisms need oxygen to maintain their metabolic process. The aquatic life depends on the Dissolved Oxygen (DO) in water for respiration. DO content shows the health and ability of the stream to purify itself through biochemical process. 'DO' also plays an important role in the precipitation and dissolution of inorganic substances in water. The levels of dissolved oxygen depend on photosynthetic activity by aquatic plants, seasons, time of the day and water flow rate (and thus on temperature). Release of sewage, decaying plants and effluents from food processing industries decrease levels of DO. The low values of dissolved oxygen affect the potability of water and can cause killing of fish and other animals of sea kingdom. DO

content of approximately 2 ppm causes the fish to disappear and shifts the environment towards anaerobic species. Good water should have solubility of oxygen about 15mg/ dm3 at 00 C and 7mg/ dm3 at 350 C. Estimation of DO is done. a) To assess quality of raw water and to keep a check on pollution. b) To test the 'Biological Oxygen Demand' (BOD) which is an important parameter to

evaluate pollutional load on waste water (refer expt. 9). c) To control the level of oxygen in boiler feed water which plays an important role in the

corrosion of boilers. Principle : Winkler Method - Oxygen present in the sample oxidizes the divalent manganous to its higher valency which precipitates as brown hydrate oxide after addition of NaOH and KI. Upon acidification the high valent manganese oxidizes iodide. (Mn reverts to divalent state) and liberates iodine equivalent to DO content of the sample. The liberated iodine is titrated against sodium thiousulphate using starch as an indicator. Note : Interference due to oxidizing agents such as NO2 (upon 0.6 mMol) and SO32- present in waste water may be eliminated by adding NaN3 to alkaline I solution. Chemical reactions involved are :

MnSO4 n2+ + SO42-

Alkaline KI + + + Mn (OH)2 White ppt (No oxygen)

Mn + 2OH + 1/2O2 MnO2 + H2O Brown ppt (Oxygen present)

MnO2 + 4H+ + 2I----- I2 + Mn2+ + 2H2O

I2 + 2Na2S2O3 Na2S4O6 + 2NaI Materials needed :

Apparatus Reagents Sample vial with lid Calibrated pasteur pipettes Reaction plate

Manganous sulphate solution Alkali iodide reagent Conc. Sulphuric acid Starch indicator Distilled water Water Samples

Note :

1. Collect the sample in a polythene bottle. 2. Measure DO within 0-4 hours of collection. Preparation of reagents : 1. Manganous sulphate : Dissolve 4.8g tetrahydrate manganous sulphate in distilled water

and dilute to 50 cm3. Filter if necessary. This solution should not give colour with starch when added to an acidified solution of potassium iodide.

2. Alkali iodide regent : Dissolve 32g of sodium hydroxide and 10g of potassium iodide

in 100 cm3 of distilled water. The solution should not give colour with starch solution when diluted and acidified.

3. Starch indicator : Dissolve 0.25g of starch power in 100n cm3 of hot distilled water.

Cool and use. Few drops of formaldehyde may be added while storing. 4. Stock sodium thiosulphate solution (0.025N). Dissolve 6.21g of sodium thiosulphate

pentahydrate in 1 dm3 of distilled water. Add a pellet of sodium hydroxide. Store in dark bottle. (1 cm3of his solution is equivalent to 0.2mg of oxygen)

5. Standard sodium thiosulphate solution : (.25 x 10-3N) Pipette out 1 cm3 of the above

stock solution in a 100 cm3 volumetric flask and make up the volume till the mark. (This solution will have to be standardized against potassium dichromate).

Procedure and observations : 1. Fill a dry sample vial (about 20cm3 capacity) with the water sample and stopper it. Tilt to

throw off excess water. 2. Add 3 drops of manganous sulphate solution and 2 drops of alkali-iodide solution

keeping the tip of the pipette below the liquid level while adding both the reagents. Stopper immediately.

3. Mix well by inverting the bottle 2-3 times and allow the precipitate to settle down.

4. Remove the stopper. Add 2 drops of conc. sulphuric acid. Mix well till the precipitate

goes into solution. They oxygen has been fixed at this stage. 5. Dispense 17 drops of the above solution in well A1 of the reaction plate using a

calibrated pipette. 6. Add 1 drop of starch into well A1. A blue colour appears. 7. Dispense sodium thiosulphate solution dropwise into well A1 using a calibrated pipette

till blue colour disappears. Count the number of drops of sodium thiosulphate solution. 8. Convert number of drops to volume as follows and enter in table 8.1. Volume in cm3 =

Number of drops x drop value of pipette. 9. Repeat steps 1 to 8 to get concordant values. Table 8.1

Trial number

Volume of water sample (cm3)

Volume of EDTA (cm3)

1 2 3

Calculations : Volume of water sample = P cm3 Volume of Na2S2O3.5H2O solution = Q cm3

# Dissolved oxygen of "DO" (in ppm) = /

Result : The amount of oxygen in the water sample is estimated to be _______________ # 1cm3 of 0.025N Na2S2O3 = 0.2 mg of O 1 cm3 of 0.025 x 10-3 Na2S2O3 = 0.2 x 10-2 mg of oxygen Q cm3 of 0.025 x 10-3 Na2S2O3 = 0.2 x 10-2 x Q mg of O2

But Q cm3 of Na2S2O3 = P cm3 of water. Therefore Pcm3 of water sample has 0.2 x 10-2 x Qmg of O2 1000cm3 (1dm3) of water

sample has

.

mg of oxygen =

mg of O2

TEST OF BIOCHEMICAL OXYGEN DEMAND (BOD) Introduction : The estimation of Biochemical Oxygen Demand (BOD) is an empirical, semi qualitative method, based on oxidation of organic matter by suitable microorganisms during a 5-day period. The degree of microbially mediated O2 consumption by organic pollutants in water known as Biochemical Oxygen Demand (BOD). It is defined as the amount of oxygen required by microorganisms to consume (oxidize) biologically decomposable organic matters in waste water under aerobic conditions. The decomposition of organic impurities in presence of bacteria results in utilization of a part of the dissolved oxygen by the bacteria during their

respiratory and metabolic activities. This depletion of oxygen is considered as a measure of the strength of water.

Organics + Oxygen B

N CO2 + H2O

All organic constituents of sewage degrade under aerobic conditions. Thus the BOD test is widely used to determine i) The pollutional load of waste waters. ii) The degree of pollution in lakes and streams at any time and their self purification

capacity and iii) Efficiency of waste water treatment methods. Materials needed :

Apparatus Reagents Sample vial with lid Calibrated Pasteur pipettes reaction plate

Manganous sulphate solution Alkali iodide reagent Sulphuric acid Starch indicator * Aereated water Water Samples

* Not provided with the kit. Note : Different Pasteur pipettes are to be used for different solutions. Procedure and observation : 1. Take three vials, A, B and C of 15 cm3 capacity and fill the vials with aerated water and

stopper without leaving any air bubble. Determine the dissolved oxygen in A immediately (refer expt. 8) by adding 1 cm3 of MnSO4 + 2cm3 of H2SO4 (avoid air passage). Let the value of "DO" be A.

2. In vial B and C, take 1 cm3 of MnSO4 solution and 2cm3 of H2SO4 solution. In vial C add

2 m of water sample. Incubate both the vials at room temperature for 5 days. 3. Find dissolved oxygen of both the bottles B (blank bottle) and C (sample bottle) by the

same method as described in experiment 8. Let the values of "DO" be B and C respectively.

Calculation :

BOD, mg/dm3 or ppm =

V

The value (A-B) suggests loss of oxygen during incubation. Note : BOD of 80mg/dm3 means that biodegradation of organic matter in a litre of sample consumes 80 mg of oxygen. Result : The amount of BOD is estimated to be ________________

*********

TEST OF IRON IN WATER Introduction : Generally iron content in surface water is very low. However, effluent from iron and steel industry lead to a high concentration of iron. When iron concentration exceeds 0.3mg/dm3 (ppm) the taste and appearance of water affected. It causes stains in clothes and ceramics. It has adverse effects on water supply structure and promotes bacteria. Excess iron content proves toxic to aquatic animals also. The permissible level for filterable iron in drinking water is 0.3 ppm.

Principle : Iron (II) reacts with 1, 10-phenanathroline to form an orange-red complex quantitatively when pH is between 6 and 9. Hydroxylamine is added to keep the iron in ferrous state. Total dissolved or Fe (II) concentrations between 0.01 and 5 ppm can be determined by this method. The detection limit is 50 ug Fe. Materials needed

Apparatus Reagents Reactions plate Calibrated Pasteur pipettes Microspatulas

Mohr's salt 1, 10 phenanthroline Ammonia (sp.gr.0.88) Hydroxyl amine hydrochloride Deionised water Water samples.

Preparation of the reagents : 1. Stock Mohr's Salt Solution : 16 mg of Ferrous Ammonium Sulphate is dissolved in

10cm3 of dil. Sulphuric acid. The volume is made up to 250cm3 with distilled water. 2. Standard Mohr's salt solution : Pipette out 10 cm3 of the stock solution and dilute to

100cm3 with distilled water. 3. 1, 10 phenanthroline : Dissolve 0.25g of 1, 10- phenanthroline in 50cm3 of distilled

water (warm if necessary). 4. Hydroxylamine hydrochloride solution : Dissolve 1.0g of the salt in 100cm3 of distilled

water. Note : Use different Pasteur pipettes for different solutions unless otherwise specified. Procedure and observations : 1. Dispense 20 drops of distilled water in well A1 18 drops of distilled water in well A2 16 drops of distilled water in well A3 14 drops of distilled water in well A4

12 drops of distilled water in well A5 10 drops of distilled water in well A6 8 drops of distilled water in well B6 2. Rinse the calibrated pipette (of step 1) with water sample. Dispense 20 drops of water

sample into well D1 using the same calibrated pipette. 3. Rinse the calibrated pipette (of step 1) with standard Mohr's salt solution. Dispense 0, 2,

4, 6, 8, 10 and 12 drops of standard Mohr's salt solution in wells A1 to A6 abd B6 respectively using the same ca calibrated pipette.

4. Dispense 1 drop of hydroxylamine hydrochloride solution in each of the above wells. 5. The pH of all the solutions should be 7. (If not adjust the pH to be 7 by adding few drops

of sodium acetate solution). 6. Dispense 3 drops of 1, 10- phenanthroline in all the above wells. Stir all the solutions by

means of microspatulas and wait for 5 minutes for the colour of the complex to develop. 7. Compare the colour developed by the water sample in D1 with that in other wells

(standard solutions). 8. Deduce the amount of iron by referring the table 10.1 (For example, if the developed

colour of the water sample matches with that in well A5, then the amount of iron in the water sample is 0.18 mg/dm3

Calculations : Concentration of iron in the standard solution = 0.906 mg/dm3 # Concentration of iron (Fe2+)

= N X .

T

The concentration (amount) of iron in various dilutions of Mohr's salt are tabulated in table 10.1

Table 10.1 Well No. A1

No. of drops of Mohr's salt solution

0

No. of drops of distilled water

20

Amount of iron (mg/dm3)

0.0

A2 A3 A4 A5 A6 B6

2 4 6 8

10 12

18 16 14 12 10 8

0.09 0.18 0.27 0.36 0.45 0.54

Result : The amount of iron in the given sample is estimated to be _____________. Note : If the colour of water sample matches with that in any of wells A1 to A4, then the water

is potable, otherwise not.

*****

TEST OF FLUORIDE IN WATER Introduction : Fluorides occur naturally in many public water supplies and, if present in excessive amount, may give rice to dental flurosis in some children. When present in much higher concentration, they may eventually cause endemic cumulative flurosis with resulting skeletal damage in both children and adults.

Fluorides are also regarded as an essential constituent of drinking water, particularly with regard to the prevention of dental caries in children. If the fluoride concentration in drinking water if a community is less than 0.5 mg/dm3, the incidence of dental caries is likely to be high. To prevent the development of dental caries in children, a number of communal water supplies are fluoridated to bring the fluoride concentration within the range as shown below. RECOMMENDED CONTROL LIMITS FOR FLUORIDES IN DRINKING - WATER

Annual average of maximum daily air temperature in 0C

Recommended control limits for Fluorides

(as F) in mg/dm3 Lower Upper

10-12 0.9 1.7 12.1-14.6 0.8 1.5 14.7-17.6 0.8 1.3 17.7-21.4 0.7 1.2 21.5-26.2 0.7 1.0 26.3-32.6 0.8 0.8

Principal : Fluoride is estimated in the water sample by colorimetric method using Zirconium Alizarin reagent. F- reacts with acid-Zr-Alizarin to form colourless ZrF62- and the dye. The colour of the dye becomes progressively weak with increase in amount of F-. Materials needed

Apparatus Reagents Reaction plate Calibrated Pasteur pipettes Microspatulas

Sodium arsenite solution Standard sodium fluoride solution Zirconium-alizarin solution Mixed acid solution Acid zirconium-alizarin reagent

Preparation of reagents : 1. Sodium arsenite solution : Dissolve 1g of sodium arsenite in water and dilute to 200 cm3. 2. Standard Sodium fluoride solution : Dissolve 0.115g of Sodium fluoride in water and

make upto 500cm3. Dilute 100 cm3 of this stock solution to 1 dm3 with water. Store in a polyethylene container. One cm3 of the solution contains 0.01mg of fluoride (as F).

3. Zirconium alizarin solution :

a) Dissolve 0.15g of Zirconium oxychloride (ZrOCl2.8H2O) in 25 cm3 of water contained in

a 25cm3 glass stopper flask. b) Dissolve 0.035g of sodium alizarin mono-sulphonate (alizarin red S) in 25cm3 of water. c) Pour solution (b) slowly in the zirconium oxychloride solution (solution a ) with stirring.

Allow standing for a few minuts to form a clear solution. 4. Mixed acid solution : a) Dilute 50cm3 of concentrated hydrochloric acid to about 200cm3 with water. b) Add 16.5cm3 of concentrated sulphuric acid to about 200cm3 of water slowly and allow

cooling. c) Mix the two acid solutions of (a) and (b). 5. Acid Zirconium-alizarin reagent : Add the mixed solution to the clear Zirconium-alizarin

solution and make upto 500cm3 with water. Mix well. The reagent changes in colour from red to yellow in an hour and is then ready for use. Store away from direct sunlight and use within six months.

Procedure and observations : 1. Dispense 0, 1, 2, 3, 4, 5, and 6 drops of standard sodium fluoride solution in wells A1 to

A6 and B6, using a calibrated pipette. Wash and dry the calibrated pipette. 2. Dispense 20 drops of distilled water in well A1 19 drops of distilled water in well A2 18 drops of distilled water in well A3. 17 drops of distilled water in well A4 16 drops of distilled water in well A5 15 drops of distilled water in well A6 14 drops of distilled water in well A6 3. Rinse the calibrated pasteur pipette with water sample. Dispense 20 drops of water

sample from step 1 into well D1, using the same calibrated pasteur pipette.

4. Add 1 drop of sodium arsenite solution in all the wells. 5. Add 1 drop of Acid-Zirconium-alizarin reagent in each of the above wells. 6. Mix thoroughly all the solutions by means of clean separate microspatulas. 7. Compare the colour developed by the water sample in D1 with that in other well

(standard solutions). 8. Deduce the amount of fluoride by referring the table 11.1 (for example if he developed

colour of the water sample matches with that in well A5, then the amount of fluoride in the water sample is

_________. Calculations : concentration of fluoride in the std. solution = 10mg/dm3 Amount of fluoride in mg/dm3 = N. NF X

T . N .

The amount of fluoride in various well are tabulated in Table 11.1

Table 11.1

Well No.

No. of drops of Sodium fluoride Solution

No. of drops of distilled water

Amount Of fluoride (mg/dm3)

A1 0 20 - A2 1 19 0.5 A3 2 18 1A4 3 17 1.5 A5 4 16 2 A6 5 15 2.5 B6 6 14 3

Result : The concentration of the fluoride in the water sample has been estimated to be _______.

TEST OF ARESENIC IN WATER

Introduction : Arsenic in widely present beneath the earth. Arsenic that comes to the surface due to agricultural irrigation and withdrawing underground water, geothermal power plants or mining, has seriously contaminated the environment, particularly in Asia. The allowed concentration of Arsenic in drinking water according to WHO's provisional guideline is .01mg/dm3. In some parts of West Bengal and Bangladesh, the concentration of Arsenic ground water ranges from 0.06mg/dm3 to 1.86 mg/dm3. Thus in these regions over 950,000 people are affected by a condition called 'arsenic dermatosis'. (blackspots, eruptions and cracking of skin) for whom ground- water is the main source of supply of drinking water. Arsenic contamination

and consequent skin cancer has also been reported. The maximum concentration of Arsenic permissible is 0.5mg/dm3 and beyond this there is no relaxation.

Principle : In ground water, arsenic usually occurs as Arsenite (As III) and arsenate (As V). Arsenic III reacts with Iodine quantitatively in presence of Sodium Hydrogen carbonate. The reaction of As III species with Iodine is as follows. H3AsO3+I2+H2O H3AsO4+2H++2I- The role of sodium hydrogen carbonate is to remove I- from the solution as fast as it is formed so that the forward reaction proceeds quantitatively.

Materials needed

Apparatus Reagents Reaction plate Calibrated pasteur pipettes

Water sample Sodium hydroxide Carbonate Potassium Iodide Iodine Starch solution.

Preparation of reagents :

1. Dissolve 0.03175g of iodine quickly in presence of about 100mg of potassium iodide and make up the solution to 250cm3. Pipette out 25cm3 of this solution into a 100cm3 flask and dilute with water upto the mark. (The has normality .00025 which should be standardized using standard Sodium thiosulphate using starch as indicator).

2. Dissolve 250mg of starch in 10cm3 of hot water. (Ref. Experiment 8) Procedure and observations : 1. Prepare about 20cm3 of saturated solution of sodium hydrogen carbonate with the water

sample to be tested. 2. Using a calibrated Pasteur pipette, dispense 2.5cm3 of the above solution into well A1. 3. Add one drop of starch solution to the same well. Stir the solution with microspatula. 4. Now using another calibrated Pasteur pipette add iodine solution in drops to well A1 with on

stant stirring till the blue colour appears. 5. Calculate the volume of iodine as follows : No. of drops of iodine X drop value of the pipette used

Calculations : (Assuming that the blue colour appears just after addition of 3 drops of I2 solution and the drop value of the pipette is 1.17), Volume of Iodine solution (V1) = 3/17 cm3 Normality of Iodine (N1) = .001 N Volume of water sample (V2) = 2.5cm3

Amount of arsenic in mg/dm3 =

.

.

1000 0.661ppm

Note : This method is not suitable to detect very low concentration of Arsenic. Concentrating the sample may improve the sensitivity.

TEST OF NITRATE IN WATER

Introduction : The amount of nitrogen in the environment is controlled by the nitrogen cycle. Inorganise nitrogen is converted to a form usable by life forms with the help of various bacteria. Use of excessive fertilizers upsets this balance of bacteria and results in an accumulation of the essential nitrogen nutrients in water. Here also this in balance results in uncontrolled marine plant growth followed by resultant eutrophication of the water bodies. These high concentrations of nitrates and nitrites are also harmful for health.

Materials needed

Apparatus Reagents - Reaction plate - Calibrated Pasteur pipettes

- Brucine solution - Conc. sulpharoc Acid - Water sample

Preparation of the Reagent :

Brucine Solution : 5 gram brucine is dissolved in 90ml. glacial acetiz acid and 10ml. distilled water.

Procedure and Observations :

1. Dispense 1 ml. of water sample in well A1 with the help of calibrated Pasteur pipette.

2. Dispense 2 drops of Brucine solution into the same well.

3. Dispense 2-3 drops of conc. sulphuriz acid into the well.

4. Shake well and wait 20 minutes for observation.

5. The solution will turn yellow in presence of nitrate.

Result : The presence of nitrate in water sample is __________

(The darker the shade, the more is the concentration of nitrate in water)

TEST OF LEAD IN WATER

Introduction :

Lead has many important industrial applications. It is used in manufacturing paints, dyes and chemicals. Lead is most widely used in the antiknock compound, tetraethyl lead, in automobiles. The exhaust fumes vehicles release this compound into the atmosphere from where it enters the water bodies. Lead also enters the domestic water supplies from conoded pipes. Lead accumulates slowly in the body as the body has no natural mechanism for getting rid of it. Lead is a slow and cumulative poison.

Materials needed

Apparatus Reagents - Reaction plate - Calibrated pasteur pipettes

- Ammonia sodium sulphite - Dithizone solution

- Chloroform

Preparation of the Reagents :

- Ammonia sodium sulphite solution : 35ml. of concentrated ammonia solution is diluted to 100ml. 0.15 gram of sodium sulphtite is dissolved in this solution.

- Dithizone Solution : 0.125gram of dithizone is dissolved in 500ml. of carbon tetrachloride (CCL4) solution.

Procedure & observations :

1. Wash the reaction plate with distilled water and dry it thoroughly.

2. Dispense 20 drops of water sample in well D1 by using a calibrated pasteur pipette.

3. Then dispense 15 drops of Ammonia sodium sulphite solution and only 2 drops of Dithizone solution.

4. Dispense 20 drops of chloroform to the above mixture.

5. Shake well and allow the phases to separate.

6. Note the colour of the lower layer.

Result : A deep orange colour indicates the presence of lead.

(This test can detect upto 4 10.6 ppm of lead)