1902-3.] Freezing-Point Depression in Electrolytic Solutions. 363 
Freezing-Point Depression in Electrolytic Solutions. By 
James Walker, F.R.S., and A. J. Robertson, B.Sc., 
University College, Dundee. 
. (Rsad December 15, 1902.) 
The following research was undertaken for the purpose of de- 
termining the freezing points of solutions under conditions which 
would involve a different systematic error from that encountered 
when the ordinary method of procedure is followed ; and, secondly, 
for the purpose of obtaining ionisation values for electrolytic solu- 
tions by the cryoscopic method which should be made by com- 
pensation as far as possible independent of any systematic error in 
determining the freezing points. 
The freezing point of a solution is the temperature at which the 
solution is in equilibrium with ice, and can only he strictly 
ascertained when the system of ice and solution is entirely isolated, 
so that the heat is neither gained nor lost by communication with 
the exterior. Such a condition is impossible to realise in practice, 
but the effects of heat transference may be so minimised as not to 
exceed the experimental errors due to other causes. 
The first theoretical discussion of the subject was given in a 
paper by Uernst and Abegg ( Zeitschrift f. pliysik. Chem ., xv. 681), 
and further contributions have since appeared in the following 
papers in the same journal : — Abegg, xx. 207 ; Raoult, xxvii. 617 ; 
Wildermann, xix. 63; xxx. 577; Loomis, xxxii. 578. Briefly, 
the account of the matter given by Uernst and Abegg is as follows. 
If the system is not isolated from the exterior, and if only liquid 
is present, the thermometer will settle at a temperature determined 
by the environment, which is called the convergence temperature. 
Ice being now added, the temperature would, if there were no heat 
communication with the exterior, reach the equilibrium tempera- 
ture of the ice and solution — that is, the thermometer would 
register the true freezing point. But the actual temperature 
registered is neither of these temperatures, hut a compromise be- 
tween them. On the one hand there is heat exchange with the 
