112 Prof. Uegnault on the Specific Heat of some Simple Bodies. 



This experiment clearly proves that iridium is always altered 

 by considerable proportions of one or more metals with low equi- 

 valents which accompany platinum, that is, palladium, rhodium, 

 and ruthenium. Palladium can scarcely be there; for it is so 

 easily attacked by aqua regia that it must go into the first 

 mother-liquors. 



Lastly, M. Debray recently offered me fused iridium ; he con- 

 sidered it to be quite free from platinum, osmium, and iridium, 

 and only suspected the presence of a little ruthenium. This 

 specimen formed a single cylinder with almost plane bases. The 

 fusion, if it had not brought about perfect liquidity, had at all 

 events produced a very complete agglomeration. The metal was 

 suspended in the apparatus by a silk thread : — 



M . . 



. 262^-78 



262^-78 



T . . 



. 98°-47 



99°*27 



& . . 



. 17°-61 



17°-18 



Ad' . . 



1°*7437 



1°-8001 



A . . 



. 395& r *58 



395s r -58 



C . . 



0-03246 



0-03273 



Mean . . . 0-03259. 



This specific heat is much less than that which I found for 

 other specimens; multiplied by the atomic weight 1233*2, it 

 gives the product 40*19, which is within the limits which I have 

 found for simple bodies. I think nevertheless that the specific 

 heat of perfectly pure iridium is below 0*0325, and that the fused 

 iridium of M. Debray still contained a little ruthenium, which 

 considerably increased the specific heat. 



Manganese. 



I formerly determined the specific heat of a carburetted man- 

 ganese (Ann. de Chim. et de Pliys. vol. lxxiii. p. 57) which had 

 been prepared by heating carbonate of manganese in a crucible 

 lined with charcoal to a strong furnace-heat. The metal was 

 very hard and brittle ; it contained more carbon and silicon than 

 cast iron ; hence its specific heat was found to be higher than 

 that which belongs to pure manganese. 



Since then I have had occasion to analyse some other spe- 

 cimens of manganese, but none of them was pure metal. M. 

 Ptousseau lent me an ingot which had been obtained by reducing 

 the natural binoxide in a lined crucible. The metal was very 

 brittle, and of a crystalline texture ; it contained much carbon 

 and silicon. I only made a single determination of its specific 

 heat. 



