On the Allui^s of Rterl SG9 



this property on it : -:^l^-^ increased the action considerably ; with 

 ■^^Q and jJ^ij it was powerful; with 10 per cent, ol'platina it 

 acted, but not with much power ; witJi 50 per cent, the action 

 was not more than with steel alone ; and an alloy of 90 platina 

 with 20 steel was not affected by the acid. 



The action of other acids on these alloys i;? similai* to that 

 of sulphuric acid, and is such as would be antici}5ated : dilute 

 mui'iatic acid, phosphoric acid, and even oxalic acid, acted on 

 the platina alloy with the liberation of more gas than from 

 zinc ; and tartaric acid and acetic acid rapidly dissolved it. In 

 tliis way chalybeate solutions, containing small portions of 

 protoxide of iron, may be readily obtained. 



The cause of the increased action of acids on this and similar 

 alloys, is, as the President of this Society suggested to us, pro- 

 bably electrical. It may be considered as occasioned by the 

 alloying metal existing in such a state in the mass, that its 

 particles form voltaic combinations with the particles of steel, 

 either directly or by producing a definite alloy, which is dif- 

 fused through the rest of the steel ; in which case the whole 

 mass W(yuld be a series of such voltaic combinations : or it may 

 be occasioned by the liberation, on the first action of the acid, 

 of particles which, if not pure platina, contain, as has been 

 sliown, a very large proportion of that metal, and which, being 

 in close contact with the rest of the mass, form voltaic combi- 

 nations with it in a very active state : or, in the third place, it 

 may result from the iron being mechanically divided by the 

 platina, so that its particles are more readily attacked by the 

 acid, analogous to the case of proto-sulphuret of iron. 



Although we have not been able to prove by such experi- 

 ments, as may be considered strictly decisi^■e, to which of these 

 causes the action is ovvhig, or how much is due to any of them, 

 yet we do not hesitate to consider the second as almost entirely, 

 if not (juite, the one that is active. The reasons which induce 

 us to sup}:)ose this to be the true cause of the action, rather than 

 any peculiar and previous arrangement of the particles of steel 

 and platina, or than the state of division of the steel, are, that 

 the two Tuetals combine in every proportion we have tried, and 

 do not, in any case, exliibit evidences of a sepaiation betw een 

 them, like those, for instance, which steel and silver exhibit ; 

 that whc;n, instead of an acid, weaker agents are used, the alloy 

 does not seem to act witli them as if it was a series of infinitely 

 miinite voltaic C()ml)inations of steel and platina, but exactly 

 as steel alone would do; that the nuiss does not render platina 

 wire more negative than steel, as it probably in the third case 

 would do ; tliat it does not rust more rapidly in a damp atmo- 

 sphere ; and that when placed in saline solutions, as muriate 



Vol.fjO. No. 'lUr,. Xuv. \H2'2. 3 A of 



