456 DAVY. 



latter, along with the hydrogen of the water in which 

 the solution was made. But a still more extraordinary 

 phenomenon was observed. If there was a liquid in- 

 terposed between the two poles and the body to be de- 

 composed, the acid, or the oxygen, was found to pass 

 through that interposed liquid to the positive pole, the 

 hydrogen and the matter of the base to the negative 

 pole, and without acting upon the substance of the in- 

 terposed liquid. Thus suppose a vegetable colour 

 tinging the water in an intermediate cup, acid will 

 pass through it without reddening it, and alkali with- 

 out making it green. Nay, an acid will pass through 

 an alkaline solution, or an alkali through an acid, 

 without uniting in either case to form a neutral salt, 

 unless the neutral compound is insoluble, for in that 

 case it falls to the bottom. But muriatic acid will 

 pass through a solution of potash, having been carried 

 over from a solution of common sea salt by the electrical 

 current, or soda will pass through muriatic acid in the 

 same circumstances, without forming in the former 

 case nitrate of potash, or in the latter nitrate of soda. 

 It was also found that the exception in the case of in- 

 soluble compounds arises from the mechanical effect of 

 their insolubility, their falling to the bottom ; for if 

 supported, as it were, on threads of any convenient 

 substance passing through the intermediate liquid in the 

 line of the electric current, the acid or alkali will pass 

 through that liquid. Thus films of asbestos conduct- 

 ing the electric stream, enabled magnesia or lime to 

 pass ; and so were the particles of metal carried over 

 when separated by the operation from nitrate of 

 silver. 



