Oxide of zinc 32.352.
When a solution of hydriodate of soda, or potass, is mixed with a solution of tile salts of manganese, nickel, or cobalt, no precipitate is obtained ; which shews that the hydriodates of these metals are soluble.
The hydriodate of soda, however, gives metallic precipi tates with the salts of copper, lead, mercury, silver, and bismuth. That of copper is whitish-grey, that of lead a fine' orange-yellow, that of protoxide of mercury greenish yellow, that of per-oxide of mercury orange-red, that of silver white, that of bismuth chesnut-brown. These are considered by Gay-Lussac, not as consisting of hydriodic acid and the oxides, but of iodine and the metals, and he therefore calls them metallic iodurets. Those chemists who adhere to the old opinions, and apply them to the sub stances now under consideration, will not allow that there is any difference corresponding to these terms, because they consider iodine as a combination of the acid with oxygen.
All the hydriodates have the property of dissolving a large quantity of iodine, which imparts to them a deep reddish-brown colour. It is separated from by boil ing, or exposure to the air in a dry state. This seems to be a simple solution, and not attended with any saturation of proper ties.
The oxiodates of the a1::alis, as was already mentioned, are formed along with the hydriodates, when iodine and tl.e alkalis are made to act on one another in water. In order to obtain these salts in a state of absolute purity, it is ne cessary to boil them repeatedly in small quantities of al cohol of a specific gravity from 8.6 to 9.2, which dissolves the hydriodates, but not the oxiodates.
Oxiodate of potass may he obtained in small crystals, nearly of a cubic form, which are not altered by exposure to the air, and deflagrate on burning coals like nitre. They require 131 times their weight of water to dissolve them. They require for their decomposition a heat somewhat higher than the hyper.oxymuriates. Oxygen is disen gaged, and ioduret of potassium (or hydriodate of potass) remains, which forms a neutral solution in water. This
decomposition affords the following proportions of con stituents : When we consider the potassium as oxydated, viz. in the state of potass, the portion of the oxygen which belongs to it is 3.773. The proportions, according to this distri bution, therefore, will be 100.000 These two last numbers give the proportions of iodine and oxygen, which form oxyiodic acid, which are as 10. to 31.321.
Oxiodate of soda crystallizes in small prisms, united in tufts, or in small cubic grains. They deflagrate on hot coals, below a red heat, giving out a very little iodine. They are nearly of the same solubility in water as the former. When decomposed by heat, they afford.
100.000 On putting iodine into a solution of soda, till the liquid begins to be coloured, fine crystals, in six sided prisms, ma) be obtained by evaporation. These are very alkaline, at.d deflagrate on burning coals. They are very soluble, and contain a large quantity of water of crystallization. Wheh soda is added to a neutral solution of oxiodate of soda, a salt is obtained in smaller crystals, or silky needles united in tufts. They are not altered by the air. Both the oxiodic and the hydriodic acids have a great tendency to form subsalts.
The oxiodates of potass and soda detonate feebly by per cussion, when mixed with sulphur. It is not probable that they could be advantageously employed in the manufacture of gunpowder ; 100 parts give only 22.59 of gas, whereas 100 parts of nitre give 53.62. This disadvantage would require to be compensated by a greater rapidity of detona tion.
Oxiodate of ammonia can only be obtained by saturating oxiodic acid with ammonia, or by saturating with it a solu tion of chlorine and iodine, (the chloruret of iodine of Gay Lussac.) This oxiodate assumes the form of small granu lar crystals. On a hot body it detonates with a hissing noise, a weak violet light, and the disengagement of va pours of iodine. When decomposed by heat, it gives out a mixture of oxygen and azote. It is composed of Oxiodic acid . . . . 100.00.