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J. Every liquid exhibiting on its surface a film of petroleum, or hydrocarbon, or containing in suspension, in 100,000 parts, more than 0.5 of such oils.

But to arrive at a fair and impartial conclusion, authorities now agree that analyses and investigations must be often, and for a prolonged period of not less than one year. The aim of modern scientists, in their analyses, is to detect the amount of organic (especially sewage) contamination. Dr. Frankland’s method is by the estimation of organic carbon and nitrogen, while Wanklyn, Chapman, and Smith reach their conclusions by estimation of nitrogenous organic matter, by breaking up the organic bodies and separating their nitrogen in the form of albuminoid ammonia. Ammonia is the measure of that portion of organic matter not decomposed but in state of or capable of undergoing putrefaction.

The maximum amount of free ammonia permissible in good drinking water is .5 of a grain per 1000 gallons, and of albuminoid ammonia .9 of a grain per 1000 gallons.