Water Testing
Q1: Describe the acidity/Alkalinity Test for Purified Water as per IP.

Ans: Boil about 50 ml of the Water in a borosilicate conical flask and allow it to cool down.

Acidity: To 10 ml of freshly cooled water, taken in a borosilicate test tube, add 0.05 ml of methyl red solution. The colour of the solution doesn’t turn red.

Alkalinity: To 10 ml of freshly cooled water, taken in another borosilicate test tube, add 0.1 ml of bromothymol blue solution. The colour of the solution doesn’t turn blue.

Q2: Describe the Ammonium Test for Purified Water as per IP.

Ans: Take two Nessler’s cylinders. Add 20 ml of Purified water in one of the cylinders. To the other one add 4.0 ml of ammonium standard solution (1 ppm) and 16 ml of ammonia free water (0.2 ppm). Now add 1 ml of Alkaline Potassium mercuri-Iodide solution to each of the cylinders. Allow to stand for 5 minutes. When viewed vertically the test solution is not intensely coloured than the standard solution.

Q3: Describe Calcium & Magnesium test for Purified Water as per IP?

Ans: To 100 ml of Purified water taken in a conical flask, add 2 ml of ammonia buffer pH 10.0, 50 mg of mordant black II mixture, and 0.5 ml of 0.01M disodium edetate solution. A pure blue colour is produced.

Q4: Describe Heavy Metal Test for purified water as per IP.
Ans: Evaporate 150 ml of purified water to 15 ml on a water bath. Take two nessler’s cylinders. To one of the cylinders add 12 ml of the test solution. To the other cylinder add 10 ml of lead standard solution (1ppm) and 2 ml of test solution and mix. Add 2 ml of acetate buffer solution pH 3.5 to each of the cylinders. Also add 1.2 ml each of thioacetamide reagent to both. Allow to stand for 2 minutes and view downwards over a white surface. The colour intensity of test solution must not be more than that of the standard solution.

Q5: Describe Chlorides test for purified water as per IP?

Ans: Take 10 ml of purified water in a test tube. To it add 1 ml of 2M nitric acid and 0.2 ml of 0.1M silver nitrate solution. The colour of the solution doesn’t change for at least 15 minutes.

Q6: Describe Nitrates test for Purified water as per IP?

Ans: Take two test tubes. Take 5 ml of water in one of the test tube. To the other test tube add 4.5 ml of nitrate-free water and 0.5 ml of Nitrate standard Solution (2ppm). Place both the test tubes in ice. Add 0.4 ml of a 10% w/v solution of Potassium Chloride and 0.1 ml of diphenylamine solution to each of the test tubes. Also add drop-wise and with shaking 5 ml of sulphuric acid to both the test tubes. Warm the test tubes on a water bath at 50°C. Allow to stand for 15 minutes. The blue colour developed in the test solution is not more intensely coloured than that of the standard solution.

Q7: Describe Sulphates test for water as per IP?

Ans: Take 10 ml of purified water in a test tube. To it add 0.1 ml each of 2M Hydrochloric acid and Barium Chloride Solution. The appearance of the solution doesn’t change for at least 1 hour.

Q8: Describe Test for Oxidizable substances for purified water as per IP?

Ans: To 100 ml of purified water add 10 ml of 1M sulphuric acid and 0.1 ml of 0.02M potassium permanganate solution and boil for 5 minutes. The solution remains faintly pink.

Q9: Describe Test for Residue on Evaporation for purified water testing as per IP?

Ans: Evaporate 100 ml of purified water to dryness on a water bath in a pre-weighed container. Dry to constant weight at 105°C. The residue weighs not more than 1 mg (i.e. 0.001%).