FE. W. Clarke on the Atomic Volume of Compounds. 17T 
sulphur having 163—16°7._ Amorphous selenium has an ato- 
mic volume of 18°6. 
Ca, 25°8. Pb, 1 
As and P 12 9, Sb. 17 ‘2, Bi215. These stand as 3:4:5. 
This Pace for P is that of the so-called “metallic” plore 
Com ae us has an atomic value of 16-9—17-0, (per- 
haps ‘UT 2, like Sb?) and the ordinary red modification 13-9— 
145. Amorphous arsenic has the value 15°9. Bo 4:1. Van- 
adium in my last paper I calculated theoretically from the ato- 
mic volume of one of its oxyds, making it equal to As an 
P. Since then, however, this idea has been overthrown, Ros- 
coe having determined the specific gravity of the metal itself 
This, 55, gives an atomic volume of 9:4, which differs widely 
* from my supposititious value, and bears no definite relation 
which I can see, to those of As an 
C {eraphite), Cae co 10. Tr 1 0 (2) Sn 165. These stand 
3. C (diamond) 3 4 Zr 21-7 (perhaps 22°0, or 
Cr, Ma, Fe, Co, Ni, U,* and Cu, 6-9 
2 Pt, Ir, Os, Pd, Ru, and Rh, 9-2 | These four values stand 
and W, 115 as 8:4:5:6. 
ca Mg and Hg, (solid) 13° 
43,+ Al 10°1— acs, Linas 30°9, Ce 16°7, In 10°2. 
have aod been traced by others. First, the alums have ee 
atomic volumes. To the evidence which has been cited by 
other Eadie th in proof of this, may now be added the ato- 
mic volumes bidiunt and cesium alums, whose specific 
padetl toni aed by. Ned tabiches show that they follow the 
rogole ule, , anumber of similar = meni oo ae 
"aa of Zn, ee Fe, and Mn, have equal atom e volum 
Tint a similar relation connects the vitriols wit aq. This 
series is especially important, since it contains the sulphates of 
Fe, Ni, Co, Mg, Zn, and Cd. Fourth, the oxyds allied to Gah- 
nite, with the general formula MO, M,0,, are, with one or two 
exceptions, equal in —— volume. Fi fth, many correspond- 
ing phosphates and arsenates have equal values. Other series 
have. been traced here se on but these are perhaps the most 
striking. 
Now, in the first place, we may lay it down as a general rule 
that when two similar elements have equal atomic volumes, the 
* Possibly this may not belong in this group, but its equal atomic volume be 
merely a coincidence. The values of some of its compounds suggest this idea. 
AS in ulated from the lower atomic weight for Gl. In my last paper I used the 
igher. 
