The Chemistry of Powder and Explosives - Sciencemadness Dot Org

428 PRIMARY EXPLOSIVES, DETONATORS, AND PRIMERS
ammonia may react with any unchanged nitrous acid which may
be present, and the hydrazoic acid may be distilled directly into
a solution of a soluble lead salt; but methods involving the distillation
of hydrazoic acid present many dangers and have not
found favor for commercial production. The alternative is to
work with materials which contain no sulfate, and to isolate the
azide by precipitation from the solution, and it is by this method
that sodium azide (for the preparation of lead azide) is generally
manufactured in this country and in England.
Hydrazine 38 reacts in alcohol solution with ethyl nitrite 39 and
caustic soda to form sodium azide which is sparingly soluble in
alcohol (0.315 gram in 100 grams of alcohol at 16°) and precipitates
out.
NH2—NH2 + C2H6ONO + NaOH > NaN3 + C2H6OH + 2H2O
The sodium azide is filtered off, washed with alcohol, and dried.
It is soluble in water to the extent of 42 grams in 100 grams of
water at 18°. It is not explosive, and requires no particular precaution
in its handling.
Azide has been manufactured in France and in Germany by
the sodamide process. Metallic sodium is heated at about 300°
while dry ammonia gas is bubbled through the molten material.
2Na + 2NH3
> 2NaNH2 + H2
The sodamide which is formed remains liquid (m.p. 210°) and
does not prevent contact between the remaining sodium and the
ammonia gas. The progress of the reaction is followed by passing
the effluent gas through water which absorbs the ammonia
and allows the hydrogen to pass; if there is unabsorbed gas which
forms an explosive mixture with air, the reaction is not yet complete.
For the second step, the sodamide is introduced into a
nickel or nickel-lined, trough-shaped autoclave along the bottom
38 Hydrazine hydrate is actually used. It is an expensive reagent procured
by distilling hydrazine sulfate with caustic soda in a silver retort. It is
poisonous, corrosive, strongly basic, and attacks glass, cork, and rubber.
Pure hydrazine hydrate is a white crystalline solid which melts at 40° and
boils at 118°, but the usual commercial material is an 85% solution of the
hydrate in water.
39 It is necessary to use ethyl nitrite or other alcohol-soluble ritrous
ester, instead of sodium nitrite, in order that advantage may be taken of a
solvent from which the sodium azide will precipitate out.