he
undissolved residue, and the latter washed with alcohol and with water, by
decantation, and then on the filter with hot water, to which a little
hydrochloric acid is added for the final washings. For ordinary work this
cellulose is dried immediately and weighed, but in exact determinations it
is washed with alcohol, again treated with 50 c.c. of the reagent, and
separated and washed as before. The cellulose thus obtained, gives no
trace of gas in the nitrometer, and duplicate determinations agree within
0.1 to 0.2 per cent. when the weight of unchanged cellulose amounts to
about 0.2 grm. Gun-cotton, which is completely soluble in acetone,
contains only traces of cellulose, and when as much as 0.85 per cent. is
present it does not dissolve entirely. This method is not applicable to
the determination of cellulose in lower nitrated products, and Dr Lunge
attributes this to the fact that these being prepared with less
concentrated acid invariably contain oxy-cellulose.

~Alkalinity.~--Five grms. of the air-dried and very finely divided sample
are taken from the centre of the slabs or discs, and digested with about
20 c.c. of N/2 hydrochloric acid, and diluted with water to about 250
c.c., and shaken for about fifteen minutes. The liquid is then decanted,
and washed with water until the washings no longer give an acid reaction.
The solution, together with the washings, are titrated with N/4 sodium
carbonate, using litmus as indicator.

~Ash and Inorganic Matter.~--This is best determined by mixing 2 or 3
grms. of the nitro-cotton in a platinum crucible with shavings of
paraffin, heating sufficiently to melt the paraffin, and then allowing the
contents of the crucible to catch fire and burn away quietly. The
temperature is then raised, and the carbonaceous residue incinerated,
cooled, weighed, &c., and the percentage of ash calculated. Schjerning
proceeds in the following way:--He takes 5 grms. of the nitro-cotton in a
large platinum crucible, he then moistens it with a mixture of alcohol and
ether, in which paraffin has been dissolved to saturation, and filtered
and mixed with one-fourth of its volume of water. Some fragments of solid
paraffin are then added, and the ether set on fire. Whilst this is in
progress the crucible is kept in an oblique position, and is rotated so
that the gun-cotton may absorb the paraffin uniformly. The partially
charred residue is now rubbed down with a rounded glass rod, and the
crucible is