GALVANISM. 



355 



deprived of their wonted properties, and that therefore they would equally pass 

 through solutions of substances for which, under ordinary circumstances, they ) 

 exhibit a strong affinity, that affinity being rendered dormant, or counteracted, 

 by the predominating influence of the electrical attraction. To reduce this 

 conjecture to the test of experiment, the water tinged with vegetable colors in 

 the intermediate cup I was replaced by a weak solution of ammonia, purified 

 water was put into the cup P, and a solution of the sulphate of potash in the 

 cup N. The sulphuric acid, attracted by the positive wire, could only reach 

 the cup P by passing through the solution of ammonia. With a battery of 1 50 

 pairs, the presence of the acid in P was manifested in five minutes by litmus 

 paper. In half an hour, the solution in P became sour to the taste, and pre- 

 cipitated solution of nitrate of baryta. Thus the sulphuric acid passed through 

 the solution of ammonia in I without producing upon it any chemical change. 

 Solutions of lime, potash, and soda, were successively substituted, with similar 

 results. 



Muriate of soda and nitrate of potash were successively placed in the cup N, 

 and the muriatic and nitric acids made to pass through concentrated alkaline 

 menstrua in 1 without any chemical effects. 



The neutral salts of lime, potash, soda, ammonia, and magnesia in solution, 

 were successively placed in the cup P, distilled water in N, and sulphuric, ni- 

 tric, and muriatic acids, successively in the intermediate cup I. The alkaline 

 elements of the salts were thus drawn through the acids, and decanted into N, 

 | without undergoing any change themselves, or causing any change in the 

 acids. 



Strontia and baryta passed freely by a similar process through muriatic and 

 nitric acids, and reciprocally these acids passed with equal facility through so- 

 lutions of strontia and baryta. The uniformity of this series of phenomena 

 was, however, broken when it was attempted to transmit the same alkalies 

 through sulphuric acid, or to pass sulphuric acid through them. A new order 

 of effects was here evolved. 



A solution of sulphate of potash was placed in the cup N, distilled water in 

 P, and a solution of baryta in I. The sulphate of potash was decomposed as 

 before, and sulphuric acid passed from the negative cup on its route toward the 

 positive wire ; but its progress was arrested in the intermediate cup, where it 

 was seized by the baryta and precipitated. It appeared, however, that this 

 obstruction to the progress of the acid was not absolutely complete ; for when 

 the process was continued for several days, traces of acid were found in the 

 positive cup. When a solution of strontia was substituted for the baryta in the 

 intermediate cup, the effects were similar. 



When the muriate of baryta was put in the positive cup, sulphuric acid in the 

 intermediate cup I, and water in the negative cup N, no alkali passed to the 

 cup N, all being arrested in I, where the sulphate of baryta was manifest, and 

 muriatic acid remained in the cup P. 



It appeared, therefore, that the exception to the transmission of the elements 

 of bodus through menstrua for which they have an affinity, includes the cases 

 in whiJu the result of that affinity would be an insoluble compound. The sul- 

 phates of strontia arid baryta are insoluble in water ; and sulphuric acid cannot 

 be transmitted, by the electric current, through strontia or baryta, nor the latter 

 through the former. 



The operation of these principles was very beautifully illustrated by the fol- 

 lowing experiment : The cups P and N were filled with solution of muriate of 

 soda, and the cup I with solution of sulphate of silver. The cup P was con- 

 nected with I by a slip of wet turmeric paper, and the cup N was connected 

 with I by a slip of wet litmus paper. When the operation of the battery com- 



