NH2  NH2 _1 L Diorthodiaminodiphenyl, <>—<>,isobtained by the reduction of the corresponding nitro

compound (obtained by the action of ethyl nitrite at o C. on metadinitrobenzidine hydrochloride) . Its tetrazo compound on reduction gives a hydrazine which, on warming with hydrochloric acid at 15o° C., decomposes into ammonium N = N chloride and, phenazone,<>—<_> (C12H2N2) . One of the most important derivatives of diphenyl, from the theoretical point of view, is diphenic acid or diorthodiphenyl carboxylic acid, which can be obtained from diparadiaminodiphenyldiorthocarboxylic acid, H1N >j—.<I > NH2, or from phenanthrene (q.v.), the consti- . HOO COOH tution of which it determines . See BENZInMNE for diparadiaminodiphenyl .