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 covered and heated for from fifteen to twenty minutes over the blow-pipe, the lid being occasionally removed.  The residue is soon converted into ash, which is weighed, and then washed out into a porcelain basin and treated with hydrochloric acid heated to 90 deg.  C. The oxide of iron, alumina, lime, and magnesia are thus dissolved, and the silica remains as insoluble residue.  The rest of the analysis is conducted according to the well-known methods of separation.  The percentage of ash as a whole is generally all that is required.