20 ELECTRO-CHEMISTRY. 



combine with the alkaline base of the salt. When, 

 however, the alkaline base passes to cup N, it there 

 unites with negative electricity, and has its alkaline 

 properties restored. If now the alkaline solution in 

 N be poured into cup I, the positive electricity of 

 the sulphuric acid will unite with the negative elec- 

 tricity of the alkali, and the base of the acid and 

 the base of the alkali will now unite and form a 

 neutral salt. 



22. When a solution of the sulphate of potash is 

 put into the cup N, distilled water in P, and a solu- 

 tion of baryta in I, the sulphate of potash is decom- 

 posed, and the base of the acid, one of the consti- 

 tuents of the salt, is attracted by the wire in P, and 

 is liberated ; but the base of the acid does not pass 

 through the solution of baryta as it passed through 

 the solution of ammonia, but combines with the base 

 of baryta, and is precipitated. How is this ? 



The base of baryta has the greatest affinity for 

 the base of sulphuric acid, insomuch that it separates 

 the base of that acid from all the alkalies and alka- 

 line earths with which it combines, namely, from 

 strontia, potassa, soda, lime, magnesia, and ammonia. 

 To account, therefore, for the precipitate in I, the 

 base of baryta having a greater affinity for the base 

 of sulphuric acid than it has for the negative electri- 



