When a solution of the iodide of potassium or sodium was used instead of the solution of salt, then double iodides were obtained: thus with lead rather a rapid formation of silky crystals occurred upon the lead, which, when examined by water, were decomposed, producing iodide of lead and solution of iodide of potash or soda. A tube two or three times the diameter of the former may be used for the experiment.
The second method of producing new combinations by weak electro-chemical powers, depends upon the electro-motive action, which is caused whenever a metal touches the oxides, or an oxide of another metal. If an oxide of a metal, a plate of metal, and a liquid be put into a tube closed at one extremity, there will be an electro-motive action of the metal with the oxide, and of the liquid with both these bodies; and the chemical effect will be according to the resultant of these three forces, which can only be ascertained by experiments.
As an illustration of the effects thus produced, three tubes, from eight to twelve hundredths of an inch in diameter, were prepared, a little protoxide of lead being put into one, deutoxide into the second, and peroxide into the third; solution of muriate of ammonia and a plate of lead were then added to each tube. After a time, lead was precipitated in the first tube, very slight chemical changes took place in the second, but a large quantity of double chloride of lead and ammonia crystallized upon the lead in the third, in the form of needles. Thus very different effects were produced, according to the state of oxidation.
Solution of salt gave similar results with the oxides of lead and lead.
The oxides of copper, with solutions of alkaline muriates, gave curious results. With muriate of ammonia, crystals were produced of considerable size, and different to those obtained by the former process. In this experiment, the black and anhydrous deutoxide of copper gradually acquired a blue colour, as if a hydrate were formed under the influence of the feeble electric current formed by the arrangement.
Copper, its deutoxide, and solution of corrosive sublimate, produced a double chloride, crystallizing in plates, and possessing a metallic lustre. [p465]
3. Crystallization of Metallic Oxides.
4. On Bromine, by M. A. de la Rive.
A few drops of bromine were then added to the water, which soon acquired a yellow colour, by dissolving a small portion of the substance; being now included in the voltaic circuit, the galvanometer needle was deviated 70°, and an abundant disengagement of gas took place from the platina wires. These were oxygen and hydrogen, in the usual proportion, proving that the water only had been decomposed.
From these experiments it results, that a body which does not at all conduct voltaic electricity, or at least but very badly, namely, pure water, may be rendered a very good conductor, by its mixture with a few drops of perfectly non-conducting substance, namely, bromine. M. de la Rive has found the same fact to occur with iodine, and iodine and water; and his father had observed, in a course of experiments made a long time ago on the conducting power of fluids, that diluted sulphuric acid is a better conductor than very much concentrated acid: may not anhydrous sulphuric acid then be a non-conductor like bromine, &c.?—Annales de Chimie, xxxv. 161.