180 



PRETENDED NEW METAL; PALLADIVM. 



The prufliates 

 do not precip. 

 platjna or mer- 



converls it into the muriate formed by the lefs oxigcnizcd acids; 

 but, (hortly after, tlie mercury is reduced to the metallic ftate. 

 Hence it was, that the alloy of platina and mercury always 

 gave a deeper coloured precipitate than platina, with muriate 

 of tin. 



Neither platina nor mercury are precipitated by pruffic acid 

 or by the prufliates. But, if fulphate, nitrate, or muriate of 

 eury fingly j but platina be poured into prufliate of mercury, an orange-coloured 

 they do jointly, precipitate is immediately formed; and, in fomc cafes, a 

 mixed folution of platina and mercury gives a fimilar pre- 

 cipitate by pruffic acid alone. 

 Platina is fimply Platina is one of the metals which are precipitated by ful-- 

 hydrogen! "^ * phuretted hydrogen, without the neceffity of a double affinity. 

 Order of affinities The affinities of platina differ much from what is generally 

 •f^iua with ^^jgj i^ jj^g tables. By the few acids I have had occafion to 

 try, oxide of platina is attraded in the following order: ful- 

 phuric, oxalic, muriatic, phofphoric, fluoric, arfenic, tartaric, 

 citric, benzoic, nitric, acetic, and boracic. 



That fulphuric acid fliould attrad the oxide of platina with 

 greater force than the muriatic, is an unanfwerable argument 

 to an opinion which was long fupported by many philofophers, 

 and which is not yet altogether abandoned by them. Muriatic 

 acid has been faid to contribute to the folution of gold or 

 platina, in nitro. muriatic acid, in the fame manner as ful- 

 phuric acid is fuppofed to promote the decompofition of water, 

 during the folution of iron by that acid diluted. The affinity 

 of muriatic acid for the oxide of gold or of platina, has been 

 looked upon as the difpoling caufc that nitric acid is decom- 

 pofed by thofe metals. But it is evident that fome other ac- 

 tion takes place; for, fulphuric acid, which has a ftron^er 

 affinity for oxide of platina frhian muriatic acid, does not in the 

 leafl: promote the decompofition of nitric acid by gold, or bj 

 platina. 



Remarkable 

 theoretical oS 

 fervatlon. 



CONCLUSION, 



^ . ^ The fubflance which has been treated of in this paper, muft 



On the nature , , . . ^ , i r 



and ufc of convmce us how dangerous it is to form a theory before we are 



general hypothc- provided with a fufficient number of fa6ls, or to fubflitute the 

 refults of a few obfervations, for the general laws of nature. 

 If a theory is fometimes ufeful, as allandard to which we may 

 refer our knowledge, it is at other times prejudicial, by creat- 

 ing 



