374 Proceedings of Royal Society of Edinburgh. [sess. 
added to the original water (p. 369). But the concentration of 
the solution at equilibrium was 0*097 normal. There was there- 
fore present at equilibrium 1T5/ 0*097 = 119 c.c. of acetic acid solu- 
tion. Now the total weight in the vessel was made up as 
follows : — 
Water . . • 
. 80 g. 
Wet ice 
. 45 
Acetic acid 
. 11*5 
Wash water . 
1 
Total, . 137*5 g. 
If from this total we subtract 119 g. as the weight of the final 
solution, we obtain 18*5 g. as the quantity of ice present at equi- 
librium. 
Experiments with M atonic Acid. 
In order to test the validity of the method for determining 
ionisation values, we made several experiments with malonic 
acid, which obeys Ostwald’s dilution law, that is, gives an 
ionisation constant when the values are determined from the 
electrical conductivity. The following numbers were obtained 
in determining this constant at 0° : — 
Malonic acid, C 2 H 4 (COOH) 2 , at 0°. 
Poo =228. 
V 
n 
m 
k 
10 
25*5 
0*112 
0*00141 
20 
36*0 
0*158 
0*00148 
33*3 
43*0 
0*189 
0*00147 
50 
52*8 
0*232 
0*00140 
Mean, 0*00144 
In the above table, v represents the dilution, /x the molecular 
conductivity in reciprocal Siemens units, m the degree of ionisa- 
tion, and k the ionisation constant calculated by Ostwald’s formula 
o 
7c— m 
(1 - m)v 
Freezing-point experiments with approximately decinormal solu- 
tions resulted as follows : — 
I. 
Depression. Concentration. 
Acetic acid .... 0*1775 0*09337 
Malonic acid . . . 0*1779 0*08445 
