26 History of physical Science from [July, 



of that in the peroxide, we should have the composition of the 

 two oxides as follows : 



Silver. 



Protoxide 100 + 4*8584 oxygen 

 Peroxide 100 + 7-2876 



Now this last number I consider as a very near approximation 

 indeed to the real quantity of oxygen in the peroxide of silver. 



The objection to the admission of this new oxide of silver is the 

 equivalent number for peroxide of silver, which we know from 

 the nitrate of silver must be very nearly 14-75 ; while the 

 sulphuret of silver and horn silver show us unequivocally that 

 the weight of an atom of silver must be nearly 13-75. Were we 

 to admit this new oxide, it would raise the weight of an atom of 

 silver to 41-25, and that of peroxide of silver to 44-25, which is 

 three times the present, and quite inconsistent with the compo- 

 sition of nitrate of silver. I am disposed, therefore, to believe, 

 that this new oxide of Mr. Faraday is merely a mixture of oxide 

 of silver and of metallic silver. Probably acetic acid, if the new 

 oxide were digested in it, would dissolve the oxide, and leave the 

 metallic portion behind. — (Journal of the Royal Institution. 

 iv. 268.) 



4. Fulminating Silver. — Mr. Faraday finds that fulminating 

 silver may be obtained from any oxide of silver, even though it 

 contain carbonic acid, by pouring over it a mixture of caustic 

 potash and ammonia. The potash absorbs the carbonic acid, 

 while the ammonia unites to the silver or its oxide. During the 

 action of ammonia on silver, there is the evolution of a quantity 

 of azote. — (Ibid.) 



5. Combination of the Chlorides with Ammonia. — Mr. Faraday 

 has published a useful set of observations on the action of 

 various chlorides on ammoniacal gas. 



(1.) Well fused chloride of calcium put into ammoniacal gas 

 rapidly absorbs it and falls into a white powder. When this 

 powder is heated, it gives out ammonia rapidly. When put 

 into chlorine, it burns spontaneously, with a pale yellow flame. 



(2.) Fused chlorides of barium and strontium absorb the gas 

 very slowly, and undergo little change in their appearance. 



(3.) Thirty grains of fused chloride of silver absorbed 40 cubical 

 inches of ammoniacal gas. The chloride fell into a white 

 powder, which blackened on exposure to the light. When 

 heated, the whole gas was given out again unaltered. When 

 placed in chlorine, it inflamed spontaneously, and the ammonia 

 was decomposed. If the chloride be not fused, it gives the 

 same compounds in a much shorter time. A strong solution of 

 chloride of silver in ammonia was left for some weeks in a phial 

 covered only by paper. Some flat rhomboidal, transparent, and 

 colourless crystals, were deposited, which appeared to be com- 

 posed of horn silver and ammonia united. This compound was 

 easily decomposed. 



