and volume of organic ions in aqueous solutions. 
3 
(2) Volume of the cation, /8-chlorethyl-trimethyl-ammonium, 
CC1H 2 . CH 2 (CH 3 ) 3 N, = C 5 H 13 C1N. 
The molecular volume of triethylamine, 
C 6 H 15 N, at 20°C = 1 38-9 
■4 Cl 0 = 21*5 
160-4 
- (CH 2 )„ = 21-2 
.-. (C 5 H 13 C1N) U = 139-2. 
Following H. Kopp = 2IT„ has been used, and since 
H u = o - 3 is used as previously, C„ = 2Hy = 10 - 6. Using these 
values and the molecular volumes of CH 3 C1, CH 2 Cl 2 , C 2 H 5 Cl, 
C 3 H 7 C1, H. 2 CC1 . C1CH 2 , CH 3 .CHC1 2 , CHC1 3i CH.CCI*, “CC1 4> 
the value 2T5 is obtained for the atomic volume of chlorine. 
Other atomic volumes given in the table have been obtained in a 
similar way. 
That these methods of calculating ionic volumes, and so values 
of a are satisfactory is shown by the agreement of the values of a 
obtained in different ways for the same ion, e.g., 
Compound used 
a , cube root of 
ionic volume 
Ion 
for calculating 
ionic volume 
Tetramethylammonium 
(ft-C 4 H 7 . H„N 
4-77 
4-72 
(C 6 H 5 H 2 N 
5-43 
T rim eth y lph eny lam m onium 
•\C 6 H 5 CH 3 HN .... 
5-40 
(C 6 H 5 (CH 3 ) 2 N 
5-35 
Other examples of this agreement will be found in the table. 
Explanation of Table. 
The table contains the ionic velocities and the data used for 
deducing the cube roots of the ionic volumes. The densities 
could not all be obtained at the same temperature, but the 
temperatures selected were in as many cases as possible the same 
for each series. In a number of cases it was possible to calculate 
the coefficients of volume expansion with temperature, and thus to 
deduce the densities at 25° C. These are indicated in the table by 
the contraction ‘ cor.’ after the temperature in the density column. 
As shown in our last paper an error in a density affects the 
product, va, in the last column of the table to about one third of 
the extent that the same error in an ionic velocity does. 
1—2 
