302 
The Chemistry of the Future. 
[July, 
theory would require. With the atomic volumes the 
periodic changes are in the opposite direction ; there is first 
a decrease and then an increase s— 
Na^gq, Mg =14, Al-10, Si = 11, P = i6, S = i6, Cl = 27. 
Tn their oxides, also, the gradation of specific gravity and 
atomic volume is to be traced. The specific gravities are— ■ 
Na g 0 = a ? 8, Mg 2 Q 2 = 37, AfiO^q-Q, Si ? 0 4 = 2*6, 
P ? 0 5 = 37 , S 2 0 q == i*g. 
Here again there is a rise, succeeded by a fall. The series 
of atomic volumes is— 
Na 3 0 = 22, Mg 2 0 3 = 22, Al 2 0 3 = 25, Si 2 0 4 =45, P 2 0 5 = 55, 
S 3 0 6 = 82. 
Here is progressive increase without a return to the original 
number. 
Speaking of alloys, M. Mendeleeff remarks that phos- 
phorus and sulphur have not quite lost the metallic character 
of the elements at the beginning of the series, since the 
phosphides and sulphides have still the aspebt of alloys. 
This feature is quite lost in the chlorides. 
Turning to another series we find the atomic weights in- 
creasing as follows 
Ag = io8, Cd = ii2, In = no, Sn — 118, Sb = i22, 
Te = i25, 1 = 126. 
Here again we have a decided metal, silver, at the head of 
the group ; an equally decided non-metallic body, iodine, at 
the end ; and in the middle an element, tin, whose metallic 
character — paradoxical as it may sound — has been ques- 
tioned on totally different grounds, and which, according to 
M. Mendeleeff ’s scheme, should bear to silicon the same 
analogy which antimony does to phosphorus, tellurium to 
sulphur, or iodine to chlorine. The foretold — but as yet un- 
discovered — element, eka-silicium, is in this case to bridge 
over the gap, as in the three parallel instances is done by 
arsenic, selenium, and bromine. 
In the silver group (No. 7) we find the specific gravities 
regularly decreasing as follows 
Ag = io*5, Cd = 8'6, In = 7*4, Sn = 7% Sb^G-y, 
Te = 6*2, 1=4*9, 
