_f._ During the generation of nitrous gas, nitrous oxide, and ammoniac, from the decomposition of solution of nitric acid in water, by tin, zinc, and iron, very complex attractions must exist between the constituents of the substances employed. The acid and the water are decomposed at the same time, and in proportions different as the solution is more concentrated, by the combination of their oxygene with the metallic body. The nitrous gas is produced by the combination of the metal with ³²/₁₀₀ of the oxygene of the acid. The nitrous oxide is most probably generated by the decomposition of a portion of the nitrous gas disengaged, by the nascent hydrogene of the water decompounded; some of it may be possibly formed from a more complete decomposition of the acid. The production of ammoniac may arise, probably from two causes; from the decomposition of the nitrous gas by the combination of the nascent hydrogene of the water, with portions of its oxygene and nitrogene at the same time; and from the union of hydrogene with nascent nitrogene liberated in consequence of a complete decomposition of part of the acid. IX. _Additional Observations on the production of Nitrous Oxide._ _a._ When nitric acid is combined with muriatic acid, or sulphuric acid,[144] the quantities of nitrous oxide produced from its decomposition by tin, zinc, and iron, are rather increased than diminished. The nitrous oxide obtained from these solutions is, however, never sufficiently pure for physiological experiments. It is always mingled with either nitrous gas, nitrogene, or hydrogene, and sometimes with all of them. [144] As was discovered by Priestley, and the Dutch Chemists. _b._ From the solutions of bismuth, nickel, lead, and copper, in diluted nitric acid, I have never obtained any perceptible quantity of nitrous oxide: the gas produced is nitrous, mingled with different portions of nitrogene. Antimony and mercury, during their solution in aqua regia, give out only nitrous gas. Probably none of the metallic bodies, except those that decompose water at temperatures below ignition, will generate nitrous oxide from nitric acid. On cobalt and manganese I have never had an opportunity of experimenting: manganese will probably produce nitrous oxide. _c._ During the solution of vegetable matters[145] in nitric acid, by heat, very minute portions of nitrous oxide are sometimes produced, always however mingled with large quantities of nitrous gas, and carbonic acid. [145] Such as the leaves, bark, and wood, of trees. When nitric acid is decompounded by ether, fixed oils, volatile oils, or alcohol, towards the end of the process small quantities of nitrous oxide are produced, and sometimes sufficiently pure to support the flame of the taper.[146] _d._ When green oxide of iron is dissolved in nitric acid, nitrous oxide is produced, mingled with nitrogene and nitrous gas.