Chemico- Galvanic Olservations. 133 



lod&ed in a fold of moist paper, become black, and colour 

 the~paper very sensibly by the formation of hydrogenated 

 gold. 



In order to explain what had taken place in this experi- 

 ment, the author hydrogenated a little, by the process indi- 

 cated, the extremity of a gold wire carefully cleaned. He 

 afterwards tried this wire upon a frog, prepared after the 

 manner of Galvani, by placing under the thighs of the 

 animal the hydrogenated extremity, and resting the other, 

 finely cleaned and polished, upon the moistened paper where 

 the spine of the back rested. The frog became very strongly 

 convulsed, and sometimes overturned the wire by its strug- 

 gles. This effect was manifested upon the frog even when 

 the gold wire had been hydrogenated, only in the weakest 

 degree, by five or six minutes action of the pile. The au- 

 thor concluded from this, that the polarity observed by Ritter 

 depended entirely upon the hydrogenation of the gold, an 

 operation which renders it positive compared to gold which 

 has not undergone it. Silver, copper, and other metals, 

 particularly antimony, have equally evinced this curious 

 phenomenon. 



(b) Hydruret of Silver and hydrogenated Silver obtained 

 ly Galvanism. 

 The author had always remarked with surprise, how two 

 wires of pure silver, submitted to the action of the two poles 

 of the pile, in water, like those of gold, were both speedily 

 converted into a gray and blackish substance. In order to 

 procure a certain quantity of this substance for examination, 

 he placed in the same vessel two large silver wires coming 

 from the two poles of a strong pile, and three lines distant 

 from each other. He left them twelve hoursin this situa- 

 tion. On the negative side the liberation of gas was very- 

 sensible, but very little of it appeared round the other wire. 

 At the expiration, of the twelve hours he found a copious 

 deposit in the recipient, and the wires were abundantly co- 

 vered with a particular substance. That of the negative side 

 was much more abundant, being of an obscure gray, swelled, 

 and full of protuberances. It was collected in a fold of 

 I 3 paper. 



