The Chemistry of Powder and Explosives - Sciencemadness Dot Org

312 SMOKELESS POWDER
The diphenylamine is converted first into diphenylnitrosamine
which is as good a stabilizer as diphenylamine itself. Since both
of these substances may be detected by simple tests upon an
alcoholic extract of a sample of the powder, the fitness of the
powder for continued storage and use may be easily demonstrated.
A strip of filter paper on which the alcoholic extract has
been allowed to evaporate is colored blue by a drop of ammonium
persulfate solution if unchanged diphenylamine is present. Likewise
the extract-, if it contains diphenylamine, is colored blue by
the addition of a few drops of a saturated aqueous solution of
ammonium persulfate. Since the alcoholic extract is often colored,
the test is best carried out by comparing the colors of two equal
portions of the extract, one with and one without the addition of
ammonium persulfate. Diphenylnitrosamine gives no color with
ammonium persulfate. One-tenth of a milligram of diphenylnitrosamine
imparts an intense blue color to a few cubic centimeters
of cold concentrated sulfuric acid. It gives no color with
a cold \fo alcoholic solution of a-naphthylamine, but an orange
color if the solution is heated. 17 None of the other diphenylamine
derivatives which occur in smokeless powder give these tests.
Diphenylnitrosamine rearranges under the influence of mineral
acids to form p-nitrosodiphenylamine. The latter substance is
evidently formed in smokeless powder and is oxidized and nitrated
by the products of the decomposition to form 2,4'- and 4,4'dinitrodiphenylamine.
Davis and Ashdown 16 have isolated both
of these substances from old powder, and have also prepared 17
them by the nitration of diphenylnitrosamine in glacial acetic
acid solution. Both substances on further nitration yield 2,4,4'trinitrodiphenylamine,
which represents the last stage in the
nitration of diphenylamine by the products of the decomposition
of smokeless powder. This material has been isolated from a
sample of U. S. pyrocellulose powder which was kept at 65° in
a glass-stoppered bottle for 240 days after the first appearance
of red fumes. The several nitro derivatives of diphenylamine may
be distinguished by color reactions with alcoholic solutions of
ammonia, sodium hydroxide, and sodium cyanide, and some insight
into the past history of the powder may be gained from
tests on the alcohol extract with these reagents, but their pres-
17 Davis and Ashdown, /. Am. Chem. Soc, 46, 1051 (1924).