Proceedings of the Royal Society of London/Volume 2/Some Experiments on a Solid Compound of Iodine and Oxygen, and on its Chemical Agencies

2567199Proceedings of the Royal Society of London, Volume 2 — Some Experiments on a Solid Compound of Iodine and Oxygen, and on its Chemical AgenciesHumphry Davy
Some Experiments on a Solid Compound of Iodine and Oxygen, and on its Chemical Agencies.By Sir Humphry Davy, LL.D. F.R.S.Read April 20, 1815.[Phil. Trans. 1815, p. 203.]

The author having observed that when a compound of iodine and chlorine was poured into an alkaline solution, there occurred a precipitate of iodine combined with oxygen, inferred that iodine would in all probability decompose the gaseous compound of oxygen and chlorine; and upon trial found this presumption confirmed. For when iodine is exposed to euchlorine at the common temperatures of the atmosphere, there is an immediate action, and the formation of two compounds, an orange-coloured liquid consisting of chlorine and iodine, and a white powder composed of iodine and oxygen.

By the application of a gentle heat, the former is made to rise in vapour, and the latter then remains as a semi-transparent white solid. It has no smell, but a strong astringent sour taste. Its specific gravity is such that it sinks in strong sulphuric acid. By heat, rather below the temperature of boiling oil, this compound is separated into its two constituents, iodine, which crystallizes on the sides of the vessel, and a gas which is found to be pure oxygen. The proportions of these products are such, that the author conceives it to consist of one portion of iodine with five doses of oxygen.

This compound has such affinity for water that it slowly deliquesces in a moist atmosphere, but remains unaltered when the atmosphere is dry. When dissolved in water, it first reddens and then destroys vegetable blues. By distillation the water rises in vapour, and by moderate heat leaves the solid substance unaltered.

The solution acts upon all metals, even upon gold and platina, and decomposes many metallic solutions, occasioning insoluble precipitates from solutions of lead or mercury, which are oxides of those metals.

It also forms compounds with all the earths that have been tried, (some of which are nearly insoluble in water,) and with alkalies it forms the same compounds that have formerly been made by other means.

This oxide also combines with acids, forming compounds which crystallize. These are intensely acid to the taste, they redden vegetable blues, and act strongly on all metals. The effects of heat upon them are various, according to the different nature of the acid with which they are combined. The nitrate and sulphate may be sublimed unaltered, but are liable to partial decomposition if too suddenly heated. The oxalate is immediately and entirely decomposed by a gentle heat, and yields iodine and carbonic acid.

Since those acids which are obtained by the decomposition of such compounds are found to be in the state of hydrates, it is evident that water is a constituent of the crystalline products.

To the compounds of iodine, oxygen, and bases, the author formerly gave the name of oxyiodes; to the new compound of iodine and oxygen, he now gives the name of oxyiodine; and to its compounds with water, oxyiodic acid. To this same compound M. Gay-Lussac has given the name of iodic acid, and for the salts he uses the generic term iodates; but to this the author objects, that hydriodic and chloriodic acids may each be as well entitled to the appellation of iodic acids as a generic name, and that the termination in at places those bodies, which he calls oxyiodes, in the common class of neutral salts, from which they differ in many respects; while the term oxyiodes expresses more definitely the nature of a combination, which has the closest analogy with the bodies termed hyperoxymuriates.