112 POLYNITRIDES.
solution of 2.5 g. of rubidium hydroxide in 3 g. of water with
concentrated hydriodic acid, add 6.2 g. of iodine, and heat until
solution is complete. On cooling, the salt separates in crystals
resembling iodine. Treat them as in the preceding preparation.
(d) Polynitrides.
- Sodium Hydrazoate NaN,,, from Sodamide NaNH 2.
Sodamide reacts with nitrous oxide to form sodium hydrazoate, the salt
of hydrazoic acid, HN 3 ; from an aqueous solution of sodium hydrazoate,
silver nitrate precipitates the difficultly soluble silver salt, a substance which
like, the pure hydrazoic aeid is extremely explosive. Hydrazoic acid, or
azoimide, was discovered by Curtius in 1890; the method of preparation given
below was devised by W. Wislicenus, in 1892. The relationship between
hydrazoic acid, iodo-hydriodic and brom-hydrobromic acids was pointed out
by Hantzsch in 1895, as well as by others.
Sodamide. Place an aluminium boat containing about 3 g. of
sodium (cf. Sodium Peroxide, No. 65) in a combustion tube;
support the tube on a row burner and heat the sodium to 300-400°
in a current of dry ammonia. Generate this gas by heating
100 c.c. of concentrated ammonia solution and dry it by passing
through a tube containing soda-lime. Hydrogen escapes from
the end of the combustion tube together with the excess of am-
monia, and the mixture can be made to burn. Sodamide must
be preserved in a well-stoppered bottle.
Sodium Hydrazoate. Place a porcelain boat containing 0.5 g.
sodamide in a combustion tube which is inclosed in an asbestos
chamber (Fig. 4, p. 3). Prepare nitrous oxide by heating 10 g. of
ammonium nitrate in a small flask; dry the gas by passing it
through a calcium chloride tube, and conduct it over the sodamide.
Then heat the combustion tube to 250° until the reaction is finished,
after which moist litmus paper is no longer turned blue by the
escaping gases.
NaNH 2 + N 2 O = NaN 3 + H 2 O,
NaNH 2 + H 2 O = NaOH + NH 3.
Silver Hydrazoate. Dissolve the sodium hydrazoate in 10 c.c. of
water; a portion of the solution, when treated with a little ferric
chloride, gives a deep brownish-red color. Acidify another and
very small portion of the solution with nitric acid, add silver
nitrate, collect the precipitate on a filter, wash it with water,
alcohol and then ether, and while the filter is still moist with ether,