CRYSTALLIZATION PRODUCED BY VOLTAIC ACTION. 497 
Ritter has 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 when 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 commu- 
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 havea 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 toapiece of anthracite or charcoal. The tube is then almost totally 
closed, only a very small aperture being left, in order 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 which 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 the plate of silver, a plate of copper be substituted, the chemical 
reaction produces electric effects which increase the energy of the afii- 
nities; the hydrochloric acid is decomposed, and there is a disengage- 
ment of carburetted hydrogen. In six months or a year after this, the 
Vot. I.—Part III. 26 
