310 F. W. Clarke on the Atomic Volumes of the Elements. 
is also a multiple of 2-6, which seems to be the starting point 
for this series. The second is also an exact multiple of 26. 
In two observations Buff obtained for the atomic volume of 
sulphuric anhydrid at its boiling point, the numbers 4418 
and 44:19. Regarding this compound as (SO,)O, and tak- 
ing Kopp’s determination of the higher value for liquid oxy- 
gen, he deduced from these numbers as the atomic volume 
of hexvalent sulphur in its liquid compounds, the value 12°, 
If, however, we take as the higher value of oxygen the altered 
number 13-0, we shall get asthe value of sulphur in (SO,)0 
the number 10-39, which agrees closely with the 10:4 above 
suggested for sulphur in the solid sulphids of iron, cobalt and 
nickel. 
The approximate equality between the atomic volumes of 
solid sulphur and selenium has often been noticed, and in my 
last paper I showed that a similar equality probably existed 
in the liquid condition, The specific gravity of crystalline 
selenium, according to Hittorf, is 4808. This gives us as its 
atomic volume, 16:5, which exceeds by 0-9 the value for octahe- 
dral sulphur. An exact equality between sulphur and selenium, 
wever, seems to me doubtful, since I have repeatedly noti 
that, as a rule, the atomic volumes of selenids slightly exceed 
those of the corresponding sulphids, and also that the selen- 
ates have values slightly in excess of the sulphates. Yet there 
are striking exceptions to this, and the point is by no means 
decided. 
Like the sulphids, many selenids have atomic volumes equal 
to the sum of those of the selenium and the metal. For the 
proto-selenid of iron we have no data, but the artificial selenids 
of cobalt and nickel, CoSe and NiSe according to Little, ges 
ane now see that in the solid condition the atomic volumes 
= : < By a3 : e i : 
relation of 1:3:3:4, and since the first three preserve th 
. My in the March No. of this Journal before I had 
; baa i ct AST ania reer nace was sent to press g 
—-NGrundlehren der Theosess sy stomic Volume of hexvalent sulphur. See Pull 
