This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
The purest form of water is obtained by converting water into a gas and then condensing it again to water. By this process all of the mineral and solid impurities are left behind. Distilled water should be used for mixing all photographic solutions, for it is only by its use that one can be absolutely certain of the most perfect results.
Water, Hard. (See Water.)
Water, Soft. (See Water.)
If a solution of silver nitrate gives a precipitate in water chlorides are present.
Dissolve good soap in alcohol; drop a few drops in a glass of water. If the water becomes milky it is hard, while if it remains clear it is soft.
Boil nut galls and add to the water. If iron is present the water will turn to a gray color. Add a pinch of red prussiate of potash; if it turns blue, iron is present.
In half a tumbler of water place a couple drops of dilute sulphuric acid and enough permanganate of potash to tinge it to a faint rose color. Cover the glass with a saucer or glass plate. If after 15 or 20 minutes the pink tinge still remains visible, the water is all right for general photographic use, yet distilled water should be used, if possible, in mixing all solutions.
Organic matter is present when permanganate does not give a permanent pink tint to the water.
Into a wide-mouthed bottle pour about one-half pint of water. Close it with a stopper or the palm of the hand, and shake violently up and down. Should an offensive odor be then detected, the water is contaminated with sewage gas.
With distilled water make a solution of silver nitrate. Carefully clean a glass and put a little of the solution in it, being sure that the solution remains transparent. Pour in some of the water to be tested. If a strong milkiness appears which is not cleared by the addition of a little diluted nitric acid, the water contains much sodium chloride.
If the addition of barium chloride gives a precipitate, sulphuric acid is present.