1818.] Oxide of Silver in Ammonia. 15 



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 crystal- 

 line form, which, however, is quickly lost by its covering the 

 whole surface of the liquor.. It is of a grey colour by re- 

 flected 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 am- 

 monia white ; carbonate, or subcarbonate more abundantly, 

 and white ; alcohol and aether throw down precipitates, at first 

 white, but rapidly changing colour ; when dry, they detonate 

 by heat or friction. Chromate of ammonia does not pre- 

 cipitate 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 com- 

 pound of protoxide of silver and ammonia. As it is frequently 

 left in the form of a black powder when oxide of silver is dis- 

 solved 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, 



