hours, and a stable collodion-cotton not more than 2 c.c. under the same
conditions. The percentage of moisture in the sample to be tested should
be kept as low as possible. A sample of nitro-cellulose containing 1.97%
of moisture gave an evolution of 2.6 c.c. per grm., while the same sample
with 3.4% moisture gave an evolution of over 50 c.c. per grm. Sodium
carbonate added to an unstable nitro-cellulose diminishes the rate of
decomposition, but if sodium carbonate be intimately mixed with a stable
nitro-cellulose the rate of decomposition will be increased. Calcium
carbonate and mercury chloride have no influence. If an unstable nitro-
cellulose be extracted with alcohol a stable compound is produced. The
percentage solubility of a nitro-cellulose in ether-alcohol rises on
heating to 132° C. A sample which before heating had a solubility of 4.7%
had its solubility increased to 82.5% after six hours' heating.

[Footnote A: _Jour. Soc. Chem. Ind._, xxiii., Oct. 15, 1904, p. 953.]

Mr A.P. Sy (_Jour. Amer. Chem. Soc._, 1903) describes a new stability test
for nitro-cellulose which he terms "The Elastic Limit of Powder Resistance
to Heat." The test consists in heating the powder on a watch glass in an
oven to a temperature of 115° C., after eight hours the watch glass and
powder are weighed and the process repeated daily for six days or less. He
claims that the powder is tested in its natural state, all the products of
decomposition are taken into account, whilst in the old tests only the
acid products are shown, and in the Will test only nitrogen, that it
affords an indication of the effect of small quantities of added
substances or foreign matters on the stability and that it is simple, and
not subject to the variations of the old tests.

Obermüller (_Jour. Soc. Chem. Ind._, April 15, 1905) considers Bergmann
and Junk's test is too complicated and occupies too much time; he proposes