lulose is
heated, and are taken at intervals of fifteen minutes for about four
hours; fresh caustic potash is added every thirty minutes or so. It is
convenient to plot the results in curves. The curves given in Fig. 53 are
from gun-cotton manufacturers in England at a private factory. The rate of
evolution of nitrogen is as follows:--

In 1 hour. In 2 hours. In 3 hours. In 4 hours.
N. N. N. N. in milligrammes.
1.25 2.55 4.5 5.75
1.5 3.25 5.25 6.75
These results are very satisfactory, the gun-cotton was of a very good
quality. Several hours are necessary to remove all the air from the
apparatus. Dr Will stated fifteen minutes in his original paper, but this
has not been found sufficient. It has not been satisfactorily proved that
Will's test can be applied to gelatinised nitro-cellulose powders. It is
convenient to plot the results in curves; the nitrogen is generally given
in cubic centimetres or in milligrammes, and readings taken every fifteen
minutes. The steepness of the curve is a measure of the stability of the
nitro-cellulose which is being examined. The steeper the curve the more
nitrogen is evolved per unit of time, and the less stable the nitro-
cellulose. In the case of unstable nitro-celluloses heated under the
conditions described, the separation of nitrogen is much greater at first
than at a later period. If the nitro-cellulose be very unstable,
explosions are produced. If the separation of nitrogen is uniform during
the prolonged heating, then the nitro-cellulose may be regarded as
"normal." If it be desired to determine the absolute amount of nitrogen
separated from a nitro-cellulose, the following conditions must be
observed:--(1.) Accurate weighing of the nitro-cellulose; (2.)
Determination of the amount of air in the CO_{2}, and deduction of this
from the volume of gas obtained; (3.) Reduction of the volume of the gas
to the volume at 0 deg. C. and 760 mm. pressure.[A]

[Footnote A: See also _Jour. Soc. Chem. Ind._, Dec. 1902, pages 1545-1555,
on the "Stability of Nitro-cellulose" and "Examination of Nitro-
cellulose," Dr Will.]

~Bergrnann and Junk~[A] describe a test for nitro-cellulose that has been
in use in the Prussian testing station for some years. The apparatus
consists of a closed copper bath provided with a condenser and 10
countersunk tubes of 20 cm. length. By boiling amyl-alcohol in the bath,
the tub