es can be kept at a constant temperature of 132 deg. C. The explosive
to be tested is placed in a glass tube 35 cm. long and 2 cm. wide, having
a ground neck into which an absorption bulb is fitted. The whole apparatus
is surrounded by a shield, in case of explosion. In carrying out the test,
2 grms. of the explosive are placed in the glass tube and well pressed
down. The absorption bulb is half filled with water, and fitted into the
ground neck of the glass tube, which is then placed in one of the tubes in
the bath previously brought to the boiling point (132 deg. C.). The evolved
oxides of nitrogen are absorbed in the water in the bulb, and at the end
of two hours the tubes are removed from the bath, and on cooling, the
water from the bulb flows back and wets the explosive. The contents of the
tube are filtered and washed, the filtrate is oxidised with permanganate,
and the nitrogen determined as nitric oxide by the Schultze-Tieman method.
The authors conclude that a stable gun-cotton does not evolve more than
2.5 c.c. of nitric oxide per grm. on being heated to 132 deg. C. for two
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 deg. 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 deg. C., after eight hours the watch glass and
powder are weighed and the process repeated daily for six days or