lulose 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.]

~The Residue~ left after treating the gelatine with ether-alcohol is, in
the case of blasting gelatine, very small, and will probably consist of
nothing but carbonate of soda. It should be dried at 100 deg. C. and weighed,
but in the case of either gelignite or gelatine dynamite this residue
should be transferred to a beaker and boiled with distilled water, and the
water decanted some eight or ten times, and the residue finally
transferred to a tarred filter and washed for some time with hot water.
The residue left upon the filter is wood-pulp. This is dried at 100 deg. C.
until constant, and weighed. The solution and washings from the wood are
evaporated down in a platinum dish, and dried at 100 deg. C. It will consist
of the potassium nitrate, and any other mineral salts, such as carbonate
of soda, which should always be tested for by adding a few drops of nitric
acid and a little water to the residue, and again evaporating to dryness
and re-weighing. From the difference in weight the soda can be calculated,
sodium nitrate having been formed. Thus--

Na_{2}CO_{3} + 2HNO_{3} = 2NaNO_{3} + CO_{2} + H_{2}O.

Mol. wt. = 106 = 170

(170 - 106 = 64) and _x_ = (106 x _d_)/64

where _