400 Sir Humphry Davy on the relations of 
but dry, was now substituted for the moist asbestus, so that 
the acid and alkali combined by capillary attraction pro- 
ducing heat ; at first, the deviation was rather less than in 
the former instance ; but as soon as the combination was 
complete, the needle stood exactly at the same point, prov- 
ing that no electricity was developed by the combination, 
any more than by the indirect communication of the acid 
and the alkali. 
After trying the effects of the contact of fluid acid upon 
platinum by the arrangement with solution of nitre, and 
finding 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 solu- 
tion 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 devi- 
ation of 7 or 8 degrees, it might be suspected that any elec- 
trical 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 
muriatic acid and solution of ammonia, which, being lighter 
