22 ELECTRO-CHEMISTRY. 



introduced into the potash, why does the capsule in 

 contact with the alkali indicate the presence of ne- 

 gative, and the slip of platinum in contact with the 

 acid indicate the presence of positive, electricity ? 



The acid, in combining with the alkali, gives off 

 its positive, and the alkali, in combining with the 

 acid, gives off its negative, electricity ; and there- 

 fore the slip of platinum in contact with the acid 

 indicates the presence of the former, and the platinum 

 capsule in contact with the alkali the presence of the 

 latter, electricity. 



25. In double decompositions, as in the case of 

 the two neutral salts when they decompose one 

 another, in which the acid base of the one combines 

 with the alkaline base of the other respectively, how 

 is it that these combinations give rise to no heat, and 

 no current of electricity ? 



When an acid and an alkali enter into combina- 

 tion and form a neutral salt, they give off their re- 

 spective electricities, heat being the product ; and 

 therefore in double decompositions, when the two 

 neutral salts decompose one another, and enter into 

 new combinations, the constituents of these salts 

 have no electricity to give off, and because of this 

 they give rise to no heat and no current of elec- 

 tricity. 



