Acetone, and acetic-ether (ethyl-acetate) may also be used as solvents for the nitro-cellulose. Another process is to boil the gun-cotton, &c., in a solution of sodium stannate made by adding caustic soda to a solution of stannous chloride, until the precipitate first formed is just re-dissolved. This solution dissolves the cellulose nitrates, but does not affect the cellulose. Dr Lunge found the following process more satisfactory in the case of the more highly nitrated products:--The reagent is an alcoholic solution of sodium-ethylate prepared by dissolving 2 to 3 grms. of sodium in 100 c.c. of 95 per cent. alcohol, and mixing the filtered solution with 100 c.c. of acetone. It has no effect upon cellulose, but decomposes nitro-cellulose with the formation of a reddish brown compound, which is soluble in water. In the determination, 5 grms. of gun-cotton are heated to 40 deg. or 50 deg. C. on the water bath with 150 c.c. of the reagent, the liquid being shaken at intervals for twenty to thirty minutes; or the mixture may be allowed to stand for a few hours at the ordinary temperature. The brown-red solution is decanted from the 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.