Galvanism, from Gaivani to Ohm. 81 



by the action of the galvanic pile in electrolysis : the opposite 

 electricities of the current invade the molecules of the 

 electrolyte, and restore the atoms to their original state of 

 polarization. 



If, as Berzelius taught, all chemical compounds are formed 

 by the mutual neutralization of pairs of atoms, it is evident / 

 that they must have a binary character. Thus he conceived a 

 salt to be compounded of an acid and an oxide, and each of 

 these to be compounded of two other constituents. Moreover, 

 in any compound the electropositive member would be replace- 

 able only by another electropositive member, and the electro- 

 negative member only by another member also electronegative ; 

 so that the substitution of, e.g., chlorine for hydrogen in a 

 compound would be impossible an inference which was 

 overthrown by subsequent discoveries in chemistry. 



Berzelius succeeded in bringing the most curiously diverse 

 facts within the scope of his theory. Thus " the combination 1 

 of polarized atoms requires a motion to turn the opposite 

 poles to each other; and to this circumstance is owing the 

 facility with which combination takes place when one of the 

 two bodies is in the liquid state, or when both are in that 

 state ; and the extreme difficulty, or nearly impossibility, of 

 effecting an union between bodies, both of which are solid. 

 And again, since each polarized particle must have an electric 

 atmosphere, and as this atmosphere is the predisposing cause of 

 combination, as we have seen, it follows, that the particles 

 cannot act but at certain distances, proportioned to the 

 intensity of their polarity ; and hence it is that bodies, which 

 have affinity for each other, always combine nearly on the 

 instant when mixed in the liquid state, but less easily in the 

 gaseous state, and the union ceases to be possible under a 

 certain degree of dilatation of the gases ; as we know by the 

 experiments of Grothuss, that a mixture of oxygen and 

 hydrogen in due proportions, when rarefied to a certain 

 degree, cannot be set on fire at any temperature whatever." j 

 And again : " Many bodies require an elevation of temperature to 



G 



