of Electrical and Chemical Changes. 99 



A piece of asbestus, of nearly the same size with the other, 

 but dry, was novv substituted for the moist asbestus, so that 

 the acid and alkali combined by capillary attraction producing 

 heat: at first, the deviation was rather less than in the former 

 instance ; but as soon as the combination was complete, the 

 needle stood exacdy at the same point, proving that no elec- 

 tricity was developed by the combination, any more than by 

 the indirect communication of the acid and the alkali. 



After trying the effects of the coQtact of fluid acid upon 

 platinum by the arrangement with solution of nitre, and find- 

 ing that oxalic acid was the acid among the powerful ones 

 which produced the slightest deviation of the needle, or the 

 smallest negative effect, I employed this acid and solution of 

 potassa, exactly in the same manner as the nitric acid in the 

 experiment just detailed ; as the joint action of the acid and 

 alkali on the platinum was only to produce a deviation of 

 7 or 8 degrees, it might be suspected that any electrical action 

 produced by combination might be more easily manifested ; 

 but no such effect occurred ; and whether the communication 

 was made by combination through dry asbestus, or through 

 asbestus wetted in a saline solution, the, effect was precisely 

 the same. 



Again,— the two surfaces of platinum were placed in con- 

 tact with strong solutions of nitre, and the communication 

 made between them by solution of potassa and nitric acid ; 

 there was no electrical action, though the chemical combina- 

 tion was intense. But when the fluids were mixed, so that a 

 little acid touched one plate of platinum and a little alkali the 

 other, electro-motion immediately began ; and in using muri- 

 atic acid and solution of ammonia, which, being lighter than 

 the saline solutions, very soon came in contact with the plati- 

 num, the effect commenced almost immediately, and continued 

 for some time to increase. 



Again, — 1 placed pieces of paper coloured with litmus and 

 turmeric, and moistened in solutions of nitre, upon two sur- 

 faces of platinum connected with the multiplier ; they were 

 covered with a stratum of porcelain clay wetted with the same 

 solution, a stratum of clay moistened with muriatic acid was 

 placed above on one plate^ and a stratum moistened with so- 

 lution of annnonia above on the other, so as to make a con- 

 tact in which there should be action upon a large surlace 

 without direct communication with the metals. In several 

 experiments of this kind there was no electro-motion ; and 

 whenever it was perceived, it was found that either the acid, 

 or the alkali, or both, had penetrated through the clay, and 

 touched the metals so as to change considerably the colour ol 



O 2 the 



