The Detection of Ammonia Production by Bacteria in Agar Slants

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Abstract
A method for detecting NH3, particularly to be used on agar slant cultures, is given. One cc. of a solution of thymol and 1 cc. of a hypobro-mite solution are added successively to the culture and allowed to act for 20 min. If NH3 is present the mixture becomes blue or greenish blue. The blue color may be extracted by means of ether, in which it is soluble, resulting in a deep red-violet color. The reaction is also given by certain aliphatic amines and by glycine. It has the advantage over the Thomas test of not using a hypo-chlorite. The hypobromite is more easily prepared fresh and of definite strength each time it is used. This is done by mixing bromine water with NaOH. Like the Thomas test, only weak solutions give the NH3 reaction.

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