Many processes have been proposed to distinguish gun cotton from ordinary cotton. One chemist has proposed to rub them in the dark; he says that gun cotton becomes luminous, whilst ordinary cotton does not give any emission of light; we have tried this process many times, and have never succeeded. The best method is the following: -

Make a mixture of 1 ounce of sulphuric ether, with 1/4 of an ounce of alcohol, introduce into it 5 or 6 grains of the cotton to try; if it dissolves and forms a syrupy solution, it indicates gun cotton, if ordinary cotton it does not dissolve. This test is the surest and most easy.

Another very serious question worth attracting attention to, is the spontaneous production of matters similar to the pyroxyle, and, like it, capable of taking fire. Mr. Thenard first called the attention of chemists to this fact. For some time, in his house, they used to deposit in an open box the snuffings of lamps, when one night they spontaneously took fire, and he attributed this effect to the fact, that the snuffings impregnated with oils had absorbed the oxygen by degrees, and had become spontaneously inflammable.

It must also be remarked, in regard to gun paper, that the liquor may unite with the nitric acid, and become inflammable. It is in this way possible to explain the spontaneous combustion which has resulted from the breaking of bottles full of nitric acid, the acid running into organic matters.