with a thin blasting gelatine.  The method of analysis is as follows:—­Weigh out 10 grms. of the substance, previously cut up into small pieces with a platinum spatula, and place over calcium chloride in a desiccator for some days.  Reweigh.  The loss equals moisture.  This is generally very small.  Or Handy’s method may be used.  The dried sample is then transferred to a small thistle-headed funnel which has been cut off from its stem, and the opening plugged with a little glass wool, and round the top rim of which a piece of fine platinum wire has been fastened, in order that it may afterwards be easily removed from the Soxhlet tube.  The weight of this funnel and the glass wool must be accurately known.  It is then transferred to the Soxhlet tube and exhausted with ether, which dissolves out the nitro-glycerine.  The weighed residue must afterwards be treated in a flask with ether-alcohol to dissolve out the nitro-cotton.

But the more expeditious method, and one quite as accurate, is to transfer the dried gelatine to a conical Erlenmeyer flask of about 500 c.c. capacity, and add 250 c.c. of a mixture of ether-alcohol (2 ether to 1 alcohol), and allow to stand overnight.  Sometimes a further addition of ether-alcohol is necessary.  It is always better to add another 300 c.c., and leave for twenty minutes or so after the solution has been filtered off.  The undissolved portion, which consists of wood-pulp, potassium nitrate, and other salts, is filtered off through a linen or paper filter, dried and weighed.

Solution.—­The ether-alcohol solution contains the nitro-cotton and the nitro-glycerine in solution.[A] To this solution add excess of chloroform (about 100 c.c. will be required), when the nitro-cellulose will be precipitated in a gelatinous form.  This should be filtered off through a linen filter, and allowed to drain.  It is useless to attempt to use a filter pump, as it generally causes it to set solid.  The precipitated cotton should then be redissolved in ether-alcohol, and again precipitated with chloroform (20 c.c. of ether-alcohol should be used).  This precaution is absolutely necessary, if the substance has been treated with ether-alcohol at first instead of ether only, otherwise the results will be much too high, owing to the gelatinous precipitate retaining very considerable quantities of nitro-glycerine.  The precipitate is then allowed to drain as completely as possible, and finally allowed to dry in the air bath at 40 deg.  C., until it is easily detached from the linen filter by the aid of a spatula, and is then transferred to a weighed watch-glass, replaced in the oven, and dried at 40 deg.  C. until constant in weight.  The weight found, calculated upon the 10 grms. taken, gives the percentage of nitro-cellulose.

[Footnote A:  If the substance has been treated with ether alone in the Soxhlet, the nitro-glycerine will of course be dissolved out first, and the ether-alcohol solution will only contain the nitro-cellulose.]