494 M. Regnault on the Specific Heat of Simple Bodies, 



might arise from the presence of a small quantity of foreign 

 metal, probably of iridium. 



Iridium, 



I have already given, in my first memoir on the specific heats 

 of simple bodies, some experiments on a specimen of iridium 

 which had been lent to me by M. de Meyendorfi^. I had found 

 for the specific heat 0*03683, which, multiplied by the equivalent 

 generally adopted, 1233-2, gave 45*43. This number being far 

 too high, I supposed that the metal was impure. 



The new specimen on which I experimented came from the Ex- 

 hibition of MM. Desmoutis, Chapuis and Co. ; it formed half of 

 a disc strongly aggregated by percussion, and weighed 509&^*21. 

 In the experiment the metal was attached by a fine steel wire. 



Mean . . . 00363. 



This value differs very little from that which I found for the 

 iridium of M. de Meyendorff. The product of the specific heat 

 by the atomic weight is 44*76, which is not comprised within 

 the limits of variation which we have observed in other simple 

 bodies. This anomaly may be explained in two ways : either 

 the metal is impure, or its atomic weight is inexact. If the 

 metal is not pure, which appears probable from the low density 

 which I found, it could only be mixed with palladium, rhodium, 

 or ruthenium ; for platinum and osmium would not change its 

 specific heat, since they have the same atomic weight. It is 

 scarcely probable that it is palladium, in consequence of the 

 chemical properties of the latter metal, and of the nature of the 

 mineral used in the preparation of iridium. It could only be 

 rhodium or ruthenium, whose atomic weights are only half that 

 of platinum ; or some metal still unknown which would be simi- 

 larly circumstanced. It is desirable that those chemists who are 

 at present engaged on the study of those metals which accompany 

 platinum, would be good enough to direct their attention to this 

 point. 



Aluminium. 



The aluminium which I employed in ray experiments was pre- 

 pared by M. Deville; it had been cast in the form of four ingots. 



