rbazide is oxidized with potassium permanganate in alkaline
solution (J. Thiele, _Ber._, 1895, 28, p. 2600). It crystallizes in
orange-red needles and is decomposed by water. The corresponding amide,
phenyl-azo-carbonamide, C_6H_5N_2.CONH_2, also results from the oxidation
of phenylsemicarbazide (Thiele, _loc. cit._), and forms reddish-yellow
needles which melt at 114deg C. When heated with benzaldehyde to 120deg C.
it yields diphenyloxytriazole, (C_6H_5)_2CN_3C(OH).

AZOIMIDE, or HYDRAZOIC ACID, N_3H, a compound of nitrogen and hydrogen,
first isolated in 1890 by Th. Curtius (_Berichte_, 1890, 23, p. 3023). It
is the hydrogen compound corresponding to P. Greiss' diazoimino benzene,
C_6H_5N_3, which is prepared by the addition of ammonia to diazobenzene
perbromide.

Curtius found that benzoyl glycollic acid gave benzoyl hydrazine with
hydrazine hydrate:

C_6H_5OCO.CH_2COOH + 2N_2H_4.H_2O = H_2O + C_6H_5CONH.NH_2 +
NH_2.NH.CH_2.COOH.

[v.03 p.0083] (Ethyl benzoate may be employed instead of benzoyl glycollic
acid for this reaction.) This compound gave a nitroso compound with nitrous
acid, which changed spontaneously into benzoylazoimide by loss of water:

C_6H_5CO.NH.NH_2 + HONO = H_2O + C_6H_5CO.N(NO).NH_2.
C_6H_5CO.N(NO).NH_2 = H_2O + C_6H_5CO.N_3.

The resulting benzoylazoimide is easily hydrolysed by boiling with
alcoholic solutions of caustic alkalis, a benzoate of the alkali metal and
an alkali salt of the new acid being obtained; the latter is precipitated
in crystalline condition on standing.

An improved method of preparation was found in the use of hippuric acid,
which reacts with hydrazine hydrate to form hippuryl hydrazine,
C_6H_5CONH.CH_2CONH.NH_2, and this substance is converted by nitrous acid
into diazo-hippuramide, C_6H_5CONH.CH_2.CO.NH.N_2.OH, which is hydrolysed
by the action of caustic alkalis with the production of salts of hydrazoic
acid. To obtain the free acid it is best to dissolve the diazo-hippuramide
in dilute soda, warm the solution to ensure the formation of the sodium
salt, and distil the resulting liquid with dilute sulphuric acid. The pure
acid may be obtained by fractional distillation as a colourless liquid of
very unpleasant smell, boiling at 30deg C., and extremely explosive. It is
soluble in water, and the solution dissolves many metals (zinc, iron, &c.)
with liberation of hydrogen and formation of salts (azoimides, azides o