The Chemistry of Powder and Explosives - Sciencemadness Dot Org

GUANIDINE NITRATE 377
The cyanamide process has made cyanamide and its derivatives
more easily available for commercial synthesis. Coke and
limestone are heated together in the electric furnace for the production
of calcium carbide. This substance, along with a small
amount of calcium chloride which acts as a catalyst, is then
heated at 800-1000° in a stream of nitrogen gas.
2CaCO3 + 5C > 2Ca CaNCN + C
The resulting dark-colored mixture of calcium cyanamide and
carbon is known as lime nitrogen (Kalkstickstoff) and is used in
fertilizers. If steam is passed through it, it yields ammonia.
CaNCN + 3H2O (steam) > CaCOs + 2NH3
Water, whether cool or warm, produces some cyanamide, which
is readily soluble, and some calcium hydrogen cyanamide, white,
microcrystalline, and sparingly soluble, but water plus acid for
the removal of the calcium (sulfuric acid, oxalic acid, or carbon
dioxide) yields a solution of cyanamide which is directly applicable
for use in certain reactions.
2CaNCN + 2H2O > Ca(0H)2 + Ca<
/NH—CN
Ca< + CO2 + H2O > CaCO, + 2NH2—CN
\NH—CN
On hydrolysis with dilute sulfuric acid it yields urea. On treatment
with ammonium sulfide it prefers to react with the hydrqgen
sulfide part of the molecule to form thiourea, not with the ammonia
part to form guanidine, and the reaction is the commercial
source of many tons of thiourea for the rubber industry. On
evaporation for crystals, the solution yields di-cyandiamide which
constitutes a convenient source for the preparation of guanidine
nitrate.
Dicyandiamide crystallizes from water in handsome flat needles
or plates which melt at 208.0-208.1° and decompose if heated
slightly above the melting point. A saturated aqueous solution
contains—