her late illness,—said to me, with evident disappointment,，
or one grain to the gallon of water. Alcohol and ether dissolve it freely, as does a solution of nitrate or hydrochlorate of ammonia and of iodides.
The density of solid iodine is 4.95; that of its vapor 8.716. It greatly resembles chlorine and bromine in its combinations, but its affinities are weaker. It does not destroy the majority of organic substances, and vegetable colors generally resist its action. It combines with several organic substances, imparting to them peculiar colors. It colors the skin brown, but the stain soon disappears.
Chloride of Iodine--Is formed by passing chlorine into a bottle containing some iodine. This can be readily done by pouring one ounce and a half of muriatic acid upon a quarter of an ounce of powdered black oxide of manganese, and heat it gradually in a flask, to which is adapted a bent glass tube. This tube must connect with the bottle containing the iodine, and the yellowish-green gas disengaged will readily combine with the iodine, forming a deep red liquid, and the operation is complete. The use of chloride of iodine will be referred to in connection with the Accelerators.
Iodides.--The iodide treated with the oil of vitriol, instantly produces a considerable deposit of iodine; and if the mixture be heated, intense violent vapors are disengaged. The reaction is due to the decomposition of oil of vitriol by iodohydric acid, water and sulphurous acid being formed, and iodine set free. The iodides in solution are decomposed by chlorine, iodine being precipitated, the smallest quantity of which in solution is instantly detected by its imparting to starch an intensely blue color.
Iodide of Potassium.*--This compound is easily made in the following manner: Subject to a moderate heat a mixture of 100 parts of iodine, 75 of carbonate of potash, 30 of iron filings, and 120 parts of water. This mass must be thoroughly dried and then heated to redness; the resulting reddish powder is to be washed with water, and the solution obtained filtered, and evaporated to dryness. It is found that 100 parts of iodine yield 135 parts of very white, but slightly alkaline, iodide of potassium.
* I shall present the preparation of only a few iodides, and such as are more intimately connected with the Daguerreotype.
Experiment.--On projecting dry pulverized iodide of potassium into fused anhydrous phosphoric acid, a violent disengagement of iodine takes place, attended by a transient ignition; fused hydrate of phosphoric acid liberates iodine abundantly from iodide of potassium; this reaction is accompanied by the phenomenon of flame and formation of a considerable quantity of hydriodic acid.
Iodide of Mercury.--For the preparation of iodide of mercury, Dublanc recommends to cover 100 grms. of mercury with 1 kilogrm. of alcohol, to add 124 grms. of iodine gradually in portions of ten grms., and agitating between each fresh addition, until the alcohol becomes colorless again. After the addition of the last 4 grms. the alcohol remains colored, the whole of the mercury having become converted into iodide. The resulting preparation is washed with alcohol; it is crystalline and of a hyacinth color.
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