BENZOPHENONE (DIPIENYL KETONE)  , C6H5'CO•C6H5, the simplest representative of the true aromatic ketones . It may be prepared by distilling calcium benzoate; by condensing benzene with benzoyl chloride in the presence of anhydrous aluminium chloride; by the action of mercury diphenyl on benzoyl chloride, or by oxidizing diphenylmethane with chromic acid . It is a dimorphous substance existing in two enantiotropic forms, one melting at 26° C. and the other at 48° C: (Th . Zincke,Berichte,1871, 4, p . 576) . It boils at 306.1° C., under a pressure of 76o.3 2 mm . It is reduced by sodium amalgam to benzhydrol or diphenyl carbinol C6H5•CHOH•CsH5; a stronger reducing agent, such as hydriodic acid in the presence of amorphous phosphorus converts it into diphenylmethane (C6H5)2.CH2 . Potash fusion converts it into benzene and benzoic acid . With phenylhydrazine it forms a hydrazone, and with hydroxylamine an oxime, which exists in one form only; if, however, one of the phenyl groups in the oxime be substituted in any way then two stereo-isomeric oximes are produced (cf . STEREO-ISOMERISM) ; thus parachlorbenzophenone oxime exists in two different forms (V . Meyer and K . F .

Auwers, Berichte, 189o, 23, p . 2403) . Many derivatives are known, thus ortho-amino-

benzophenone, melting at 1o6° C., can be obtained by reduction of the corresponding nitro compound; it condenses under the influence of heated lead monoxide to an acridine derivative and with acetone in presence of caustic soda it gives a quinoline . Tetramethyl-diamido-benzophenone or Michler's ketone, CO[CsH4N•(CH3)2)2, melting at 173°, is of technical importance, as by condensation with various substances it can be made to yield dye-stuffs . It is prepared by the action of carbonyl chloride on dimethyl aniline in the presence of aluminium chloride: COC12±2C6H5N(CH3)2=2HC1+CO[C6H4N(CH3)2]2 .