Physical Relations of Osmium. 305 
obtained as a perfectly compact mass, the apparent volatility of 
the metal being due doubtless to previous oxidation, the cru- 
eibles used being permeable to air. We have seen, as regards 
arsenic and antimony, that their oxides are more volatile than the 
metals themselves. 
It was lately stated that osmium may be obtained in crystals b 
the same means as those used for boron and silicon, but I have 
as yet seen no account of the form which it assumes. 
Deville has furnished another interesting fact with respect to 
osmium, by determining the density of the vapour of osmic acid, 
which he has found = 8°88. This, if we take the generally 
received atomic weight for osmium, gives the atomic volume 
131-6 
8°88 
calculate back to the theoretical atomic weight, we get (14-57 
x 8:88) —32=97°38, a number closely approaching 97, which, 
as we have seen, brings the equivalent of osmium into simple 
and harmonious relation with those of the other elements of the 
arsenic group. 
The specific gravity of fused metallic osmium having been 
lately determined by Deville = 21:4, there can be little doubt 
that all the metals of the platinum family possess the same atomic 
volume when in the free state, about 4°6 or 4°7: the specific 
gravity of ruthenium is not yet known with accuracy, but such 
experiments as have been made render it improbable that it will 
prove an exception. This number is about one-fourth the mean 
of the atomic volumes of the long-recognized members of the 
arsenic group; but these latter differ so widely among them- 
selves*, that the comparison is of little or no value. It would 
be desirable to get a good determination of the density of osmic 
acid in the solid state, so that its atomic volume might be caleu- 
lated and compared with that of antimonious acid. 
The specific heat of osmium, so far as its value as a physical 
character goes, oppuses the introduction of this element into the 
arsenic group. It has been determined by Regnault ='03063 ; 
multiplying now by the equivalent 97, we have the product 
29711, thus placing osmium in the list of the elements (inclu- 
ding the majority), for which the product of specific heat by 
= 14°82, indicating a condensation to 2 vols. If we now 
31 
% Phosphorus’ }) ie... ++ T-83 (Schritter) =16°94. 
; 75 he 
AYSENIC 2.000% Wi>d'tens) 67 (Haruniath) =13'23. 
Antimony ss. oid vee Me =17°76 
67 (Karsten) 
; 207 
B th peseeoseonesss —— (Marchand =21°" Ze 
ay) 9°83 &Scheerer) : 
