ut 
J. W. Mallet on Osmious Acid. 61 
It is lately stated that osmium may be obtained in crystals by 
e same means as those used for boron and silicon, but I have 
as Na seen no account of the form which it assumes. 
eville has furnished another interesting fact with respect to 
osmium, by determining the density of the vapor of osmic acid, 
which he has found = 8°88. This, if we take the generally 
received atomic weight for osmium, gives the atomic volume 
Bib 199, indicating a condensation to 2 vols. If we now 
calculate back to the theoretical atomic weight we get (14°57X 
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 ar- 
senic 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 at. vols. of the long recognized members of the arsenic 
group, but these latter differ so widely among themselves* 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 at. vol. might be calculated and compared 
with that of antimonious acid. 
The specific heat of osmium, so far as its value as a physical 
character goes, opposes the introduction of this element into the 
arsenic group. It has been determined by Regnault =-03068 ; 
multiplying now by the equivalent 97, we have the product, 
29711, thus placing osmium in the list of the elements (includ- 
ing the majority) for which the product of sp. ht. by at. wt. is 
nearly 3, while for phosphorus, arsenic, antimony and bismuth 
the product thus baited is twice as great, or about “6. In this 
, however, osmium probably resembles nitrogen—the lat- 
ter examined, as it necessarily is, in the gaseous form. 
_Itis to be hoped that the conducting power for heat and elec- 
ticity of compact osmium will soon be examined; nothing is as 
yet known of these characters. , 
aengiat ncn ee a ne oe 
Arsenic, CE ets sai (Herapath) see ce 
en eae, oe =i (Kariten) aL 
Hess panda 
