______________________|
| | | |
| | _Solution_-- | _Residue_-- |
| | Hexa-nitro-cellulose | Dry and weigh, ignite |
| | (Gun cotton). | and reweigh. Loss = |
| | | _Cellulose_. |
| | |_________________________|
| | | |
| | | Residue consists of |
| | | sawdust, charcoal, |
| | | coal, chalk, guhr, |
| | | or mineral matter, &c. |
|______________________|______________________|_________________________|

NOTE.--Camphor is found by difference. Sulphur is only partially soluble
in ether. It is better, therefore, to extract some of the original
substance with water, and treat residue with alcoholic KHO. Add bromide,
acidify, and precipitate as BaSO.

~The Solubility Test.~--The object of this test is to ascertain, in the
case of gun-cotton, the percentage of soluble (penta and lower nitrates)
cotton that it contains, or in the case of soluble cotton, the quantity of
gun-cotton. The method of procedure is as follows:--Five grms. of the
sample which has been previously dried at 100 deg. C., and afterwards exposed
to the air for two hours, is transferred to a conical flask, and 250 c.c.
ether-alcohol added (2 ether to 1 alcohol). The flask is then corked and
allowed to digest, with repeated shaking, for two or three hours. The
whole is then transferred to a linen filter, and when the solution has
passed through the filter, is washed with a little ether, and pressed in a
hand-screw press between folds of filter paper. The sample is then
returned to the flask, and the previous treatment repeated, but it will be
sufficient for it to digest for one hour the second time. The filter is
then again pressed first gently by hand, then in the press, and afterwards
opened up and the ether allowed to evaporate. The gun-cotton is then
removed from the filter and transferred to a watch-glass, and dried in the
water oven at 100 deg. C. When dry it is exposed to the air for two hours and
weighed. It equals the amount of gun-cotton and unconverted c