CRYSTALLIZATION PRODUCED BY VOLTAIC ACTION". 427 



Ritter lias likewise asserted, that if, for the purpose of decomposing 

 water, we employ a fragment of tellurium as a negative conductor, the 

 hydrogen which comes into contact with it combines with the metal, and 

 produces a brown powder or hydruret of tellurium. But M. Magnus, 

 who examined this product, ascertained that it was composed of tellu- 

 rium in its state of greatest division. 



Hydrogen and carbon, which combine in different proportions when 

 they are in their nascent state, (since all animal and vegetable substances 

 in decomposition give out carbonated hydrogen,) must also be capable 

 of combining at the negative pole of the pile. This property is of 

 great importance in electro-chemistry, especially m hen it is required to 

 deprive a body of its carbon. The following experiments will serve to 

 show the use that can be made of anthracite, that is to say, of carbon 

 almost pure, and of ordinary carbon, in the researches in which we are 

 engaged. 



When we plunge into an acid, in contact with a metal, a piece of 

 anthracite or charcoal, a current is produced, the direction and intensity 

 of which depend on the chemical action of the liquid on the charcoal 

 and the metal. Let us, for instance, take a piece of charcoal freed from 

 all foreign matter, and attach it to one end of a platina wire in comnm- 

 nication with the multiplier, and then plunge it into nitric acid, which 

 also communicates with the galvanometer by means of another platina 

 wire. We then have a current from the carbon to the acid : this result 

 shows that the carbon has been attacked by the acid. 



A pair of carbon and copper plates plunged into hydrochloric acid, 

 determines a current, which proceeds from the copper to the carbon, in 

 consequence of the slow action of the acid on the metal. A pair of 

 carbon and silver plates acts in a similar manner : whence we derive 

 a very simple process for forming chloride of silver and copper. Into 

 a glass tube closed at one end, we pour concentrated hydrochloric acid, 

 and plunge into it a plate of silver, attached by a wire of the same 

 metal to apiece of anthracite or charcoal. The tube is then almost totally 

 closed, only a very small aperture being left, in oi'der to afford a vent to 

 the gas which escapes in the reaction of the bodies upon each other. The 

 following is the result : the silver being the positive pole of the small pile, 

 attracts the chlorine and combines with it, while the hydrogen goes to 

 the carbon, with whicli it forms a gaseous combination, which escapes. 

 When the tube is hermetically sealed, the tension acquired by the gas 

 soon causes it to burst. The chloride of silver that had been formed is 

 dissolved, and, when the acid is saturated, this compound crystallizes in 

 beautiful translucid octahedrons of one or two millimetres in length. If, 

 for tiie plate of silver, a plate of copper be substituted, the chemical 

 reaction produces electric effects which increase the energy of the afS- 

 mtics; tlie liydrocliioric acid is decomposed, and there is a disengage- 

 ment of carburctted iiydrogen. In six months or a year after this, the 



Vol. I — Paut III. 2 g 



