BENZOPHENONE. 385 



oxidation of sulphobenzy lie aldehyde (p. 319) colorless 

 needles, united in fascicles, which, under the influence 

 of heat, decompose without melting. 



Dithiobenzoic acid, C 6 H 5 .CS.SH. The potassium 

 salt is formed by mixing henzotrichloride (p. 275) with 

 an alcoholic solution of potassium sulphite. The free 

 acid is a heavy, violet, very unstable oil. 



ACETONES. 



Benzophenone (Diphenylketone), C 13 H 10 = C 6 H 5 . 

 CO.C 6 H 5 , is formed, together with benzene, by the 

 destructive distillation of calcium benzoate. Is also 

 formed by heating mercury-phenyl (p. 272) with ben- 

 zoyl chloride. Colorless, rhombic prisms, insoluble in 

 water, easily soluble in alcohol. Fuses at 48, and 

 boils at 295. Hydrogen, in statu nascendi, converts it 

 into benzhydrol (p. 316). Under certain conditions, 

 the nature of which is not understood, a second modi- 

 fication of benzophenone is formed. This fuses at 26- 

 26.5, and appears to belong to the monoclinic system. 

 It is very easily converted into the rhombic modi- 

 fication. The reverse transformation has not been 

 observed. 



Methylbenzophenone, C' 4 II 12 = C 6 H S .CO.C 6 H 4 . 



CH 3 . Is formed, together with benzoylbenzoic acid, 

 by the oxidation of benzyltoluene with a mixture of 

 potassium bichromate and dilute sulphuric acid. 

 Colorless oil, of a weak aromatic odor; insoluble in 

 water, easily soluble in alcohol or ether. It boils at 

 307-312. Yields benzoylbenzoic acid (p. 322) by 

 oxidation. 



Acetpphenone (Methylphenylketone), C 6 IP.CO.CH 3 . 

 Is obtained by distilling a mixture of calcium benzo- 

 ate and acetate ; and by the action of benzoyl chlo- 

 ride on ziiicmethyl. Colorless, large, crystal plates. 

 Fusing point, 14 ; boiling point, 198. Treated with 



