ic acid and phosphorus, but sodium in the presence of amyl
alcohol reduces it to tetrahydrodiphenyl C12H14.

Many substitution derivatives are known: the monosubstitution
derivatives being capable of existing in three isomeric forms. Of the
disubstitution derivatives the most important are those derived from
diparadiaminodiphenyl or benzidine (q.v.).

_Orthoaminodiphenyl_,

NH2
__ |__
/ \__/ \ ,
\__/ \__/

is prepared by the action of bromine and caustic soda on
orthophenylbenzamide (R. Hirsch, _Berichte, 1892, 25_, 1974); when its
vapour is passed over heated lime, carbazol (q.v.) is formed.

_Diorthodiaminodiphenyl_,

NH2 NH2
__| |__
/ \__/ \ ,
\__/ \__/

is obtained by the reduction of the corresponding nitro compound
(obtained by the action of ethyl nitrite at 0 deg. C. on
metadinitrobenzidine hydrochloride). Its tetrazo compound on reduction
gives a hydrazine which, on warming with hydrochloric acid at 150 deg.
C., decomposes into ammonium chloride and _phenazone_,

N = N
__| |__
/ \___/ \
\__/ \__/

(C12H8N2). 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,
__ __
H2N / \__/ \ NH2 ,
\__/ \__/
| |
HOOC COOH

or from phenanthrene (q.v.), the constitution of which it determines.
See BENZIDINE for diparadiaminodiphenyl.

DIPHILUS, of Sinope, poet of the new Attic comedy and contemporary of
Menander (342-291 B.C.). Most of his plays were written and acted at
Athens, but he led a wandering life, and died at Smyrna. He was on
intimate terms with the famous courtesan Gnathaena (Athenaeus xiii. pp.
579, 583). He is said to have written 100 comedies, the titles of fifty
of which are preserved. He sometimes acted himself. To judge from the
imitations of Plautus. (_Casina_ from the [Greek: Kleroumenoi],
_Asinaria_ from the [Greek: Onagos], _Rudens_ from some other play), he
was very skilful in the construction of his plots. Terence also tells us
that he introduced into the _Adelphi_ (ii. 1) a scene from the [Greek:
Synapothneskontes], which had been omitted by Plautus in his adaptation
(_Commorientes_) of the same play. The style of Diphilus was simple and
natural, and his l