138 



TRANSACTIONS OF THE 



substituted a copper spiral wire for the slip of lead, and 

 in six weeks after, I observed a white layer upon the 

 sulphuret of silver, which I thought to be chloride of 

 silver ; but it did not become black on exposure to the 

 sun, nor dissolve in ammonia, as Professor Bache found 

 on the application of this substance. 



We next dissolved it in cold nitric acid, which dis- 

 engaged nitrous gas, till the black sulphuret underneath 

 made its appearance, and the solution yielded the reac- 

 tions of sulphuric acid, magnesia and silver, proving 

 that not only the white layer had been dissolved, but 

 also the thin film of native silver formed below, which 

 was observed before by the streaks I made in the white 

 layer. It seems then that this was nothing more than 

 the sulphuret of magnesium, the magnesium having 

 taken the sulphur of the sulphuret of silver, and of 

 course the silver had been reduced. The oxygen of the 

 dissolved magnesia passed to the copper wire, which 

 was reduced to a black powder of deutoxide. The so- 

 lution of the small bottle was uncolored until it became 

 green, when exposed to the air, by the green submu- 

 riate of copper which was formed. It did not contain 

 any sulphuric acid. 



This reduction of the sulphuret of silver, as well as 

 the preceding, with a solution of nitrate of copper, and 

 a copper spiral, which was read before the philosophi- 

 cal society on the 5th of November, 1830, and printed 

 in their transactions, seems to me fully to demonstrate, 

 that the Mexican amalgamation is an electro-chemical 

 process. 



