Urea \U"re*a\, a. [NL. See Urine.] (Physiol. Chem.) A very soluble crystalline body which is the chief constituent of the urine in mammals and some other animals. It is also present in small quantity in blood, serous fluids, lymph, the liver, etc. Note: It is the main product of the regressive metamorphosis (katabolism) of proteid matter in the body, and is excreted daily to the amount of about 500 grains by a man of average weight. Chemically it is carbamide, CO(NH2)2, and when heated with strong acids or alkalies is decomposed into carbonic acid and ammonia. It unites with acids to form salts, as nitrate of urea, and it can be made synthetically from ammonium cyanate, with which it is isomeric. Urea ferment, a soluble ferment formed by certain bacteria, which, however, yield the ferment from the body of their cells only after they have been killed by alcohol. It causes urea to take up water and decompose into carbonic acid and ammonia. Many different bacteria possess this property, especially Bacterium ure[ae] and Micrococcus ure[ae]}, which are found abundantly in urines undergoing alkaline fermentation.

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