The presence of ammonia in water in small quantities is normal. This nitrogenous substance exists either in a free state or what is known as albuminoid ammonia, that is, soluble protein matter. Whenever a water is found to contain an exceptionally high content of ammonia in either one of these forms, a suspicion of contamination is justifiable. The contamination is of an organic character, that is of sewage or animal wastes or decaying vegetable or animal matter.

The presence of free ammonia in small quantities of course is not objectionable to health. That is not the point which is important. The significant feature of the presence of excessive amounts of these bodies is in the probability of contamination just mentioned.