401 
electrical and chemical changes. 
than the saline solutions, very soon came in contact with the 
platinum, the effect commenced almost immediately, and con- 
tinued for some time to increase. 
Again,— I 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 
solution of ammonia above on the other, so as to make a con- 
tact in which there should be action upon a large surface 
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 of 
the papers, which were placed as indications of the correct- 
ness of the experiment. 
Having brought forward what appear to me decided proofs 
on this subject, I shall now proceed to investigate the opera- 
tion of the metals and fluids in combinations containing two 
of the latter substances. At first I was surprised to find that 
platinum acted so powerfully with nitric acid, which under- 
goes no chemical change by contact with it, and suspecting 
that it might arise from the presence of minute portions of 
muriatic acid or muriatic salts, I took great pains to exclude 
these substances by washing the platinum in distilled water, 
not touching it with the hands, & c. but when the conditions 
were those of perfectly clean and pure platinum and perfectly 
pure nitric acid, the phenomena were the same. Similar 
