[142] The decomposition and recomposition of water, in this process, are analogous to some of the phænomena observed by the ingenious Mrs. Fulhame.
[143] From one of Dr. Priestley’s experiments, it appears that hydrogene gas is sometimes disengaged during the solution of iron in very dilute nitric acid by heat. This phænomenon has never occurred to me.
[144] As was discovered by Priestley, and the Dutch Chemists.
[145] Such as the leaves, bark, and wood, of trees.
[146] As I have observed after Priestley.
[147] As was discovered by Priestly.
[148] This deep color depended, in some measure, upon the nitro-muriatic vapor suspended in it. I have since observed that it is more intense in proportion as the heat employed for the production of the gas has been stronger. The natural color of the peculiar gas is deep yellow.
[149] The decomposition of aëriform nitrous acid by mercury, was first noted by Priestley; vol. iii. pag. 101. This decomposition I have often had occasion to observe. In reading Humbolt’s paper on eudiometry, Annales de Chimie, xxviii, pag. 150, I was not a little surprised to find that he takes no notice of this fact. He seems to suppose that nitrous acid can remain aëriform, and even be condensed, in contact with mercury, without alteration. He says, “In mingling 100 parts of atmospheric air with 100 of nitrous air, the air immediately became red, but all the acid produced remained aëriform; and after eighteen hours some drops only of acid were formed, which swam upon themercury.”
[150] Lavoisier has said concerning aqua regia, “In solutions of metals in this acid, as in all other acids, the metals are first oxydated, by attracting a part of the oxygene from the compound radical. This occasions the disengagement of a particular species of gas not hitherto described, which may be called nitro-muriatic gas. It has a very disagreeable smell, and is fatal to animal life when respired; it attacks iron, and causes it to rust; it is absorbed in considerable quantities by water.” Elem. Eng. 237.
[151] I have no doubt but that the gas procured from the solution of gold in aqua regia, is analogous to that produced from platina.