Sottas—On the Law of Gladstone and Dale. 161 
Then for Na-O-N;—O- we have :— 
Na Ne 0. 
4°89 + 3198 + 5°56 
5B 4 ODT oe 
and 
ne = low OIC ys est 
Src eee = 2005) = ane 
= 2°693. 
Again, for N,-O- we have :— 
Nz O 
F132 = 2:18 
Raa oka = 0 2274 = Ke 
and 
ne -1 0:33853 |. neha 
de = 1-474, 
The study of atomic volumes has rendered it highly probable 
that the sum of the atomic volumes of the constituents of a 
compound is equal to the total volume of the compound, and if 
this be so the sum of the partial volumes (7. e. of the groups 
Na-O-N,-O- and N,-O) should be equal to the volume of the 
whole salt NO;Na. 
Thus we have :— 
m  63°4 
N;0.Na, om = 3-693 SOS 23 04, 
m, 21:6 
N,0, Gh L474 = 2 = 1465, 
and 23°54 + 14°65 = 38:19, while the volume found by dividing 
the molecular weight (85) of the whole salt by the density (2°246) 
is 37°85, a sufficiently close approximation. 
The question will now arise whether or not some other distri- 
bution of the atoms in the molecule would not have afforded as 
equally an exact agreement. In order to decide this I have 
treated the molecule in a variety of ways, some probable, some 
the reverse, but in no case does such a close correspondence between 
the sum of the partial volumes and that of the whole salt result. 
If true for sodium nitrate our treatment should also hold in 
SCIEN. PROC. R.D.S., VOL. VIII., PART I. M 
