[48] In this experiment, as well as in the last, some of the mixture was thrown into the jar undecompounded. EXP. _c_. Five grains of charcoal, and 20 of nitre, were now fired in the same manner as before, the mercury being covered with a stratum of water. After the precipitation of the vapor on the introduction of oxygene, no red fumes were perceived. EXP. _d_. 30 grains of nitre, 5 of charcoal, and five of silicious earth,[49] were now mingled and fired. The gas received under mercury was composed of 18 carbonic acid, and nearly 12 nitrogene.[50] A little muriatic acid was poured on the residuum in the tube; a slight effervescence took place. [49] To detach the potash from the carbonic acid. [50] This nitrogene contained a little nitrous gas, as it gave red fumes when exposed to the air. The free nitrous acid was decomposed by the mercury, as it was not covered with water. EXP. _e_. The top of the mercury in the jar was now covered with a little diluted muriatic acid, and a small glass tube filled with a mixture of 3 grains of charcoal, and 20 nitre. After the deflagration, the tube itself with the residuum it contained, were thrown into the jar. The carbonic acid was quickly detached from them by the muriatic acid, and the whole quantity of gas generated in the process, obtained; it measured 15 cubic inches. 4 cubic inches of it exposed to solution of potash, diminished to 1⁴/₁₀; 7 of the remainder, with 8 of oxygene, gave only 12. EXP. _f_. 60 grains of nitre, and 9 of charcoal were fired, the top of the mercury in the jar being covered with water. After the deflagration, the tube that had contained them was introduced, and the carbonic acid contained by the carbonate of potash, disengaged by muriatic acid. 30 measures of the gases evolved were exposed to caustic potash; 20 exactly were absorbed, the 10 remaining, with 10 of oxygene, diminished to 17. EXP. _g_. A mixture of nitre and charcoal were deflagrated over a little water in the mercurial jar: after the precipitation of the vapor, the water was absorbed by filtrating paper. This filtrating paper, heated in a solution of potash, gave a faint smell of ammoniac. EXP. _h_. Water impregnated with the vapor produced in the deflagration, was heated with quicklime, and presented separately to three persons accustomed to chemical odors. Two of them instantly recognised the ammoniacal smell, the other could not ascertain it. Paper reddened with cabbage juice was quickly turned green by the vapor. These experiments are sufficient to shew that the decomposition of nitre by charcoal is a very complex process, and that the intense degree of heat produced may effect changes in the substances employed, which we are unable to estimate.