1902 - 3 .] Freezing-Point Depression in Electrolytic Solutions. 365 
but this is allowed for in fixing the temperature of the external 
bath, which is adapted to a certain uniform rate of stirring. 
If we consider the other factor which determines the difference 
between the true and apparent freezing points — namely, the rate of 
formation or fusion of ice — it is evident that this rate depends,, 
first, on the quantity or proportion of ice present ; second, on the 
fineness of its state of division— together, on the surface of contact 
between the ice and solution. For a given quantity of solution,, 
the more ice we take and the more finely we divide it, the more 
rapidly will the equilibrium temperature be restored after any 
disturbance, and the more closely will the apparent and true 
freezing points coincide. In the present research it has been 
specially our effort to reduce the error arising from the finite 
time required for this restoration to a minimum by employing 
an amount of ice as great as circumstances would permit. 
In practically all previous researches ice has been introduced 
into a solution of known concentration by slightly overcooling the 
solution, and then inducing crystallisation by inoculation with a 
minute fragment of ice on the end of a wire or capillary, A 
certain quantity of ice then separates in correspondence with 
the degree of overcooling, but this quantity is of necessity 
small if the equilibrium concentration of the solution is to 
be accurately known, for as ice separates from the solution 
the concentration increases, and it is the equilibrium concen- 
tration alone with which we are concerned. In Raoult’s ex- 
periments, the ice which separated was only about one-half 
per cent, of the weight of the solution. In many other cases 
the amount of ice did not exceed 02 per cent. In our own 
experiments the minimum proportion of ice was 12 per cent., 
the average being about 15 per cent. 
Of course, when such large proportions of ice are present, it 
is impossible to ascertain the equilibrium concentration of the 
solution from the initial concentration. We therefore adopted 
the expedient previously employed by Roloff (Zeitsclirift f. physikal. 
Chem., xviii. 572) for concentrated solutions, and filtered off the 
solution from the ice after equilibrium had been attained, the 
concentration being then determined by analysis. 
The ice which we used was prepared by freezing distilled water. 
