AM IDES are a group of organic compounds, derived, under certain conditions, from ammonia or NIIIIII), by the exchange of one or more atoms of hydrogen for a corresponding number of atoms of a metal. or a compound radical. The first of these compounds that was discovered was that in which one atom of hydrogen was replaced by one of potassium (NIIIIK, or NII2K), the product being regarded as a compound of (aatidogen) with potassium, and being termed amide of potassium. At present, the term wittily is restricted to the case in which one or more atoms of hydrogen are replaced by an acid radical, and the amides are called primary, secondary, or tertiary, according as one, two, or all three of the atoms of hydrogen arc replaced by the acid radical. The primary amides may be obtained in various ways, of which we shall mention two: (1.) If we heat an ammoniacal salt, two atoms of water are given off, and the amide corresponding to the acid is left; thus, acetate of ammonia water = acetamide which, expressed typically, is C41130, N, where is the radical of acetic acid. (2.) If an anhydride is submitted
Ii to the action of ammonia, there are simultaneously formed an amide and an ammoniacal salt. Thus. valerianic or valerie anhydride (0,011.03)2+ ammonia (NIL.), = valerate of ammonia valeramide 0,0119(N112)02 , which, expressed typically, is II N, where is the acid radical of valeric acid. The amides are, for the II most part, capable of being obtained in a crystalline form, and are fusible volatile bodies. For a description of the more complicated forms of amides, and for a history of their general properties, the reader is referred to the article "Amides" in Watts's Dictionary of Cheatiyirg, and to the chapter on Amides in the 2d edition (1867) of Naquet's Principe* de (,Annie, vol. ii. pp. 844-368. If, in place of an arid radical, it base radical replaces our or more atoms of hydrogen in ammonia, a class of compounds, termed amines, is formed. whose composition is noticed in the article ORGANIC BASE.S.