304 Prof, J. W. Mallet on the Chemical and 
the former the more fusible and volatile body, the latter the 
stronger acid. In addition, we have some cases of the prot- 
oxide (MO), a feeble base, and the binoxide (MO*), a body of 
still more feebly basie properties, verging upon the acids. All 
other grades of oxidation, so far as they exist at all, may per- 
haps be correctly viewed as compounds of the preceding inéer se. 
The stability of the oxide (MO%) in the separate state is remark- 
able; its formula is one of rare occurrence. 
The affinity of all the elements of the group for oxygen is 
considerable ; it is so even in the case of osmium and ruthenium, 
usually placed among the noble metals. Dumas (Traité de Chim. 
app.) states that osmium does not oxidize at common tempera- 
tures, nor even at 100° C.; but Ihave obtamed conclusive evi- 
dence that oxidation may go on slowly even at the ordinary 
atmospheric temperature. The paper label and the cork of a 
tube containing pure metallic osmium have in the course of se- 
veral years become blackened, precisely as organic matter is by 
the fumes of osmic acid, the black tint on the paper decreasing 
from the mouth of the tube along the outside. A piece of white 
paper, in which some black platinum residue had been wrapped, 
was strongly stained in the immediate neighbourhood of the pow- 
der in the course of a few weeks. The same effect is distinctly ob- 
servable even upon the paper label placed inside a tube of native 
iridosmine (Siberian) in the usual coarse grains—a specimen which 
has lain among other minerals, and has never been placed near 
any artificial preparations of osmium. Osmium, like arsenic and 
antimony, is clearly capable of slowly taking up oxygen at com- 
mon temperatures, At a red heat, roasting in a current of air 
affords, as is known, a good method of obtaining osmic acid from 
the iridosmine of platinum residues—just as by similar roasting 
arsenious acid is prepared from the native arseniurets. 
It would be a matter of much interest to compare osmium with 
its supposed homologues under circumstances in which we should 
expect it to play an electro-negative part. Fremy has announced 
his belief in the existence of an osmiuretted hydrogen; but such a 
body has not yet been isolated and described. Compounds of 
the metal with ethyle, methyle, &c., would be well worth exami- 
nation ; and it is not unlikely that such might be prepared from 
a body which in some states of combination exhibits such a high 
degree of volatility. 
The earlier experiments of Deville and Debray upon the pla- 
tinum metals seemed to have shown that both osmium and ru- 
thenium could be volatilized, at exceedingly high temperatures, 
without previous fusion; if this were confirmed, a strong point 
of resemblance with arsenic would be made out ; but it appears 
from a more recent paper, that osmium at least may be fused and 
