The Chemistry of Powder and Explosives - Sciencemadness Dot Org

DETERMINATION OF NITROGEN 269
upon the absorption of the gas in caustic soda solution and the
titration of its acidity is now often used instead.
There are many other variations of the heat test. 101 They are
sometimes called stability tests, but most of them, it will be
noted, involve the self-catalyzed decomposition of the sample in
an atmosphere of air or of red fumes. They indicate the comparative
stability only 6f materials which are physically alike.
True indications of the stability of nitric esters are to be secured
only by studying the decomposition of the substances in vacuum.
For this purpose the 120° vacuum stability test is most generally
preferred.
Ash in nitrocellulose is determined by gelatinizing the sample
with acetone which contains 5% of castor oil, setting fire to the
colloid, allowing it to burn tranquilly, and igniting the charred
residue to constancy of weight. It is sometimes determined as
sulfate by dissolving the sample in pure concentrated sulfuric
acid and igniting to constant weight.
Nitrogen in nitrocellulose is determined by means of the
nitrometer, an instrument of great usefulness to the chemist who
is working with nitric esters or with nitroamines.
Determination of Nitrogen
Nitric acid and organic and inorganic nitrates, and in general
all substances which contain free nitric acid or yield nitric acid
when they are treated with concentrated sulfuric acid, are analyzed
by means of the nitrometer. The method depends upon
the measurement of the volume of the nitric oxide which is produced
when concentrated sulfuric acid acts upon the sample in
the presence of mercury. It is satisfactory also for the determination
of nitro group nitrogen in certain nitroamines, in nitroguanidine
and in tetryl but not in methylnitramine. It is not
satisfactory in the presence of mononitro aromatic compounds
or of other substances which are nitrated readily by a solution of
nitric acid in concentrated sulfuric acid.
101 U. S. War Department Technical Manual TM 9-2900 and the U. S.
Bureau of Mines Bulletin* on the analysis of explosives describe the standard
heat tests in detail. "Explosives, Matches, and Fireworks" by Joseph
Reilly, New York, D. Van Nostrand Company, Inc., 1938, pp. 71-83, describes
about 40 different heat tests.