Determination of sulfate and chloride in water treatment plant

 ANALYSIS OF SULPHATE IN WATER

Standard E.D.T.A. - (.01M) : 

Dissolve 3.7274 gm of disodium slat of ethylene Diamine Tetra Acetic Acid  (EDTA), after drying at 80 c for 1 hour, in 1000 ml of de-ionised water and mix well.

Hydrochloric Acid (1:24) :

Mix one part of con. Hydrochloric Acid and 24 parts of the de-ionised water.

Sulphate Buffer : 

Mix 113 ml of ammonium hydroxide, 8.252 gm of ammonium chloride, 7.44 gm of E.D.T.A. and 4.060 gm of magnesium chloride (mg Cl2. 6H2O) and make up the volume to 1000 ml with de-ionised water.

Sulphate indicator : 

• Mix 0.5 gm of Eriochome Black T or Solochrome Black and 100 gm. of sodium chloride and grind thoroughly.
• Take 25 ml. of water sample in a 250 ml. conicle flask. Add 1cc of 1:24 Hydrocloric Acid and boil.
• Add 15 ml of barium chloride (0.01M) and boil well to precipitate all sulphate in water as barium sulphate. Cool the flask.
• Take 10 ml. of de-ionised water in a 500 ml flask and add 5 drops of sulphate buffer and a pinch of sulphate indicator. The colour of the solution becomes red, titrate it with .01M E.D.T.A. till the colour changes to blue.
• To the above solution add the solution obtained above the colour of the solution becomes red, titrate again with  .01M E.D.T.A. till the colour changes to blue.

Calculations:

Sulphate present in water sample in parts per million (P.P.M.).

Total hardness X Sample taken in ml + BaC12 so1. added in m1

1000

Total hardness of the water is to be determined by titrating 25 ml of the sample water against .01M E.D.T.A. using eriochrome black - T indicator. Titer value x 10 = total hardness in parts per million (ppm).

ANALYSIS OF CHLORIDE IN WATER

• Potassium Chromate Indicator - Dissolve 5 gm of potassium chromate in 100 ml demineralised water.
• Dilute Nitric Acid - Dilute 1 ml of conc. HNO3 to 100 ml with demineralised water.
• Standard Silver Nitrate Solution (N/100) - Dissolve 1.6988 gm of silver nitrate crystals after drying for one hour at 105oC in 1000 ml. of demineralised water.
• The 100 ml water sample solution in which P alkalinity and M alkalinity have been determined is used for chloride determination.
• Add 2 drops of dil. HNO3 and 5 ml of Potassium chromate solution to the above solution and titrate against N/100 AgNO3 until the colour changes to reddish brown.
• Report chloride in parts per million (ppm) using the formula -
• Volume of N/100 AgNO3 solution consumed x 3.55 = Chloride in ppm (parts per million).

ANALYSIS OF HARDESS OF WATER.

Standard EDTA solution 0.01 M - 

 Dissolve 3.7275 gm. of EDTA (after drying at 80oC) and make up the volume to 1000 ml. with demineralised water.

Ammonia Buffer Solution - 

Dissolve 67.5 gm. NH4CL, 570cc Ammonia 0.93 gm. of EDTA and 0.616 gm. MgSO4 in 950 ml demineralised water.

Solochrome Black (Erio - chrome Black - T) : 

• Weigh 0.5 gm of indicator powder and 100 gm sodium sulphate and grind thoroughly to make fine powder.
• Take 10 ml. demineralised water in a 500 ml. conical flask add 4 drops of Ammonia buffer solution and a pinch of Solochrome indicator. Titrate with std.EDTA till the solution becomes blue.
• Take 100 ml of the water sample to be tested in the same flask .The colour of the sample becomes red. Titrate it with std. EDTA till the colour changes to blue.
• Calculate the total hardness in water in ppm using the formula-
• Hardness in parts per million (ppm) = reading of 0.01 M EDTA in ml x 10.

ANALYSIS OF NITRATE IN WATER

KMnO4 (0.1N) - 

Dissolve 3.30 gm of KMnO4 crystals in 150 ml demineralised water. Heat the solution for some time and keep at low heat till fully dissolved. Cool the solution and filter through  cotton. Add 850 cc demineralised water to make it  1000 cc.

Standardisation Of KMnO4 With Oxalic Acid :  

Weigh accurately 1.575 gm pure oxalic acid into a 250 ml volumetric flask and make up the volume to      250 cc with demineralised water .Take 20 ml of this oxalic acid into a flask, add 2 to 3 cc of A.R. sulphuric acid and heat to 60o - 70o C. Titrate with KMnO4 solution till the colour changes from colourless to pink. 20cc of oxalic acid should consume 20 cc of KMnO4.

2% v/v H2SO4 : 

Take 980 cc of demineralised water in a 1000 cc measuring flask and add 20 cc of conc. H2SO4 and mix well. 

For High Nitrite : 

• Take 100 cc of 2% V/V H2SO4 in a 500 cc Flask, add 2.5 cc of 0.1N KMnO4 solution and warm upto 40o - 50o C . Now titrate against the sample, taken in a burrette, till the permanganate colour just vanishes.
• Now divide 5750 by the burrette reading to get the nitrite content in ppm.

Low Nitrite : 

• Take 100cc of sample in a 500ml flask add 10cc.of distilled water and 100cc of 2% v/v H2SO4 titrate against N/10 KMnO4 till the colour persists for one minute.
• Burete Rdg x 23 gives the nitrite content in water in ppm (parts per million).