For the production of nitrous oxide in quantities not exceeding 20 quarts, a mode still more simple than that I have just described may be employed. The salt may be decomposed by the heat of an argands lamp, or a common fire, in a tubulated glass retort, of 20 or 30 cubic inches in capacity, furnished with a long neck, curved at the extremity; and the gas received in small airholders. Thus, if the pleasurable effects, or medical properties of the nitrous oxide, should ever make it an article of general request, it may be procured with much less time, labor, and expence,[96] than most of the luxuries, or even necessaries, of life. [96] A pound of nitrate of ammoniac costs about 5s. 10d. This pound, properly decomposed, produces rather more than 34 moderate doses of air; so that the expence of a dose is about 2d. What fluid stimulus can be procured at so cheap a rate? DIVISION IV. _EXPERIMENTS and OBSERVATIONS on the COMPOSITION of NITROUS GAS, and on its ABSORPTION by different bodies._ I. _Preliminaries._ In my account of the composition of nitric acid, in Division I. I gave an estimation of the quantities of oxygene and nitrogene combined in nitrous gas: I shall now detail the experiments on which that estimation is founded. At an early period of my researches relating to nitrous oxide, from the observation of the phænomena taking place during the production of this substance, I had concluded, that the common opinion with regard to the composition of nitrous gas, was very distant from the truth. I had indeed analysed nitrous gas, by converting it into nitrous oxide, before I attempted to ascertain its composition by immediately separating the constituent principles from each other: and my first hopes of the possibility of effecting this, were derived from Dr. Priestley’s experiments on the combustion of pyrophorus in nitrous gas, and on the changes effected in it, by heated iron and charcoal. This great philosopher found, that pyrophorus placed in contact with nitrous gas, burnt with great vividness, whilst the gas was diminished in volume to about one half, which generally consisted of nitrogene and nitrous oxide. He likewise found, iron heated by a lens in nitrous gas, increased in weight, whilst the gas was diminished about ½, and converted into nitrogene.[97] He heated common charcoal, and charcoal of copper,[98] in nitrous gas by a lens. When common charcoal was employed, the gas was neither increased or diminished in bulk, but wholly converted into nitrogene; when charcoal of copper was used, the volume was a little increased, and the gas remaining consisted of ⁵/₇ nitrogene, and ²/₇ carbonic acid. [97] Experiments and Observations, vol. II. pag. 50. Last Edition. [98] That is, charcoal produced by the decomposition of spirits of wine. Vol. II. pag. 39.