IQO Sir H. Da\y o» the Relations 



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 cliemical change by contact with it, and suspecting 

 that it might arise from the presence of minute portions of 

 muriatic add 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 

 reasonings may be applied to solutions of potassa, soda, &c. 

 which do not chemically alter platinum by contact, and yet 

 render it positively electrical with respect to platinum in water 

 or saline solutions. It must however be called to mind that 

 the oxygen in nitric acid, and the metals in the alkalies, have 

 attractions of a very decided kind for platinum ; and in taking 

 the scale of electro-negative bodies, solutions of chlorine, or 

 nitro-muriatic acid, produce a more powerful electrical effect 

 on platinum than nitric acid, nitric acid than muriatic, and 

 muriatic than sulphuric. 



When platinum is brought in contact with an acid, the pole 

 touching the acid is negative, the opposite pole is positive, as 

 I have found by the condensing electrometer; and the reverse 

 is the case when it touches an alkali ; so that the circulation 

 of the electricity is from the metal to the alkali, and from the 

 acid to the metal. 



Rhodium, iridium, and gold, act in combinations consisting 

 of acid and alkali, on which they have no chemical effect, ex- 

 actly like platinum; the surface of the metal in the solution 

 of alkali benig positive, that in the solution of the acid, nega- 

 tive. With silver and palladium the electricity is greater, 

 particulai'ly if nitric acid is used; and with charcoal and oxi- 

 dable metals, there is the same general result, the action being 

 in general exalted in proportion as the chemical attractions 

 are stronger, provided tliere are no interfering circumstances : 

 and in combinations of this kind niti'o-muriatic acid is more 

 active than nitric, and the order is after, nitric, nitrous sul- 

 phuric, phosphoric, vegetable acids, sulphurous, prussic, sul- 

 phuretted hydrogen ; and, with the alkalies, potassa, soda, 

 baryta, ammonia, and so on. 



It is always to be understood that strong or concentrated 

 solutions of acids and alkalies are employed; for in cases 



where 



