In one experiment, 5.40 grains of nitrate of potash yielded 4.975 cubic inches of gas, at 60°F, and barometer 30 inches. The residue not absorbed by the sulphate of iron, was 0.015 cubic inch, leaving 4.96 cubic inches of nitric oxide = 1.594 grains NO², and which correspond to 2.869 grains nitric acid, or 53.13 of the nitrate of potash. Four consecutive experiments yielded 53.13 53.14 53.73 53.29 ——— Mean 53.32 or leaving out the third experiment. Mean 53.19 The calculated percentage of nitric acid in nitrate of potash, the acid being represented by 6.75, and the potash by 5.8992, is 53.36. THOMSON gives for percentage of nitric acid in nitrate of potash 52.94, and BERZELIUS 53.44. Salts in powder, which are difficult to pass through mercury without loss, may be enclosed in small glass cylinders. Nitro-Glycerin may be made into pellets with powdered glass, and congealed at 45°F, or simply congealed by taking great care it is not partially thawed during manipulation. Mr. Theron Skeel, of Albany, has furnished me with the following extract from the Engineering Journal of the 17th Nov., 1871, being an explanation of M. L. Hote’s method of analysing the gases produced by the explosion of Nitro-Glycerin. He uses Ure’s graduated electric eudiometer, made out of a green glass organic analysis tube. Introduce into the apparatus ten centimeters of the gases evolved from water by voltaic electricity, then introduce small globules of thin glass, containing from five to six milligrammes of the explosive; an electric spark being passed through the mixed gases by means of the platina points melted in the upper part of the eudiometer, explodes the gases, breaks the small glass globules and explodes the Nitro-Glycerin. The gases evolved are colorless, and contain a proportion of binoxide of nitrogen. Submitted to the proper absorbents, for moisture, binoxide of nitrogen and carbonic acid, there remains nitrogen. Thus: 1 gramme Nitro-Glycerin gave at temp. 0 Cent. 29.7 barom. press., of these gases 284 c.c. One hundred parts by volume contained Carbonic acid, 45.72 Binoxide of Nitrogen, 20.36 Nitrogen, 33.92 ——— 100.00 MARTIN[6] has devised a method of ascertaining the percentage of nitric acid, by its conversion into ammonia. Nitric acid when mixed with sulphuric or muriatic acids, in the presence of metallic zinc, is converted into ammonia (Gmelin I, 828). By placing some zinc in a mixture of the two acids, there is no disengagement of gas, whilst the nitric acid is converted into ammonia. Hydrogen in its nascent state combines with the oxygen of the nitrogen compound, produced by the nitric acid alone.