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 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.

Obermueller (Jour.  Soc.  Chem.  Ind., April 15, 1905) considers Bergmann and Junk’s test is too complicated and occupies too much time; he proposes to heat gun-cotton to 140 deg.  C. in vacuo, and to measure continuously by means of a mercury manometer the pressure exerted by the evolved gases, the latter being maintained at constant volume; the rate at which the pressure increases is a measure of the rate of decomposition of the nitro-cellulose.