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1818.] There is every reason, therefore, to believe this a protoxide of silver, containing about two-thirds the quantity of oxygen found in the common oxide, or that obtained by precipitation from the nitrate; and there are also other circumstances observable in its solution and during its formation which favour this notion.

When this oxide forms on the surface of an ammoniacal solution by slow spontaneous evaporation, it takes a crystalline form, which, however, is quickly lost by its covering the whole surface of the liquor. It is of a grey colour by reflected light, and highly resplendent; the light transmitted through thin films is of a bright yellow colour. When heated gradually it is reduced, giving off oxygen without change of form; but heated suddenly, it fuses first, and leaves a solid button of silver: under pressure, it perhaps might be fused without decomposition.

Potash precipitates the solution of oxide of silver in ammonia white; carbonate, or subcarbonate more abundantly, and white; alcohol and æther throw down precipitates, at first white, but rapidly changing colour; when dry, they detonate by heat or friction. Chromate of ammonia does not precipitate until nitric acid be added. Tincture of galls gives a very copious black precipitate, different in appearance to that obtained from the nitrate of silver by adding ammonia after the tincture. Solution of iodine in water gives a brown curdy precipitate, but with nitrate of silver a yellow turbidness. Muriatic acid or muriates always form chloride of silver.

It is probable, from these circumstances, that part of the silver exists in the solution in the state of protoxide, and as no gas is given off during the solution of the original oxide, that a portion of nitric acid and water have been formed.

M. Berthollet has in the paper before referred to, described a fulminating compound of silver and ammonia, obtained from solutions similar to those from which the above oxide had been obtained, and has stated it to be his opinion that it is a compound of protoxide of silver and ammonia. As it is frequently left in the form of a black powder when oxide of silver is dissolved in ammonia, I imagined it might be a compound of the peroxide with the alkali, as protoxide was formed and held in solution; and that the circumstance of the liberation of azote,