Intelligence and Miscellaneous Articles, 395 



The most strongly calcined osmium, much less alterable than the 

 osmium obtained at a low temperature, changes into osmic acid at 

 ordinary temperature*; at the highest temperatures osmic acid is 

 always obtained. 



Ruthenium behaves altogether like osmium. The strongly cal- 

 cined metal oxidizes in a muffle at a temperature scarcely above 

 400° C, and volatilizes in great quantity. In what form, it is dif- 

 ficult to say ; for the material then exhales the odour of ozone, the 

 formation of which always accompanies the decomposition of hy- 

 perruthenic acid. The product deposited in the muffle is always 

 the binoxide of ruthenium. This oxide sublimates and crystallizes 

 in a porcelain tube traversed by a current of oxygen in which 

 substances containing ruthenium are heated. M. Eremy thus 

 proved its volatility, and discovered the means of extracting directly, 

 and under the most beautiful forms, some products of the roasting 

 of osoiide of iridium. Ruthenium also, which in the metallic state 

 is one of the most fixed substances we know, evaporates very 

 quickly in a muffle, especially at a very elevated temperature f. 



These properties absolutely distinguish osmium and ruthenium 



* The characteristic smell of osmic acid is at length perceptible in 

 bottles containing even crystallized osmium prepared at a high tempera- 

 ture. The stoppers then become covered with the black coating given by 

 the reduction of osmic acid. 



t By operating on a few grams of ruthenium we have been able in a 

 few hours to volatilize 24 per cent, of its weight in a highly heated muffle ; 

 in the blowpipe flame the volatilization is much more rapid and still 

 more considerable in amount. 



From the fact that osmium and ruthenium volatilize very rapidly in the 

 oxyhydrogen flame of the blowpipe, giving osmic acid and binoxide of 

 ruthenium, it must not be concluded that these oxides are undecomposable 

 by heat. Osmic acid would be reduced, in the interior of the flame at 

 that high temperature, to sesquioxide of osmium, crystallizable in golden- 

 coloured scales, which we have made known. The final result would still 

 be the same : this oxide, on coming into the air, into a relatively cold 

 region, would there be changed into osmic acid. In supposing that the 

 oxide of ruthenium is not decomposed into a lower oxide, it is not neces- 

 sary also to admit that it is absolutely undecomposable at the temperature 

 of 2500° given by the combustion of hydrogen and oxygen. This com- 

 bustion is not complete in the hottest parts of the flame ; hydrogen and 

 oxygen exist there uncombined ; and if the oxide of ruthenium has a less 

 tension of dissociation than that of water at this high temperature, one 

 can conceive that it may not be decomposed. Oxide of ruthenium would 

 therefore be less readily decomposable than water by heat. To discover 

 whether it is really undecomposable, we must be able to heat it (as we 

 have pointed out forthe oxide of iridium) in a vacuum to high temperatures j 

 but, unfortunately, there exist no vessels suitable for such experiments. 

 The hypothesis of the very great stability of the oxide of ruthenium, 

 however, is supported by the fact that this oxide, heated in a porcelain 

 tube, exhibits (like the oxide of iridium), at least at a bright red heat, no 

 sensible tension of dissociation ; it merely volatilizes, and is deposited in 

 the form of crystals and a coating of binoxide in the colder parts of the 

 porcelain tube. 



