BY MIXTURES OF ELECTROLYTES.—BARNES. 147 
bath kept constantly at 0° the temperature of the water in the 
freezing-tubes at first fell rapidly, then more slowly, till it 
remained constant at 0.05°. This experiment was repeated with 
the same result, and thus the convergence temperature was 
shown to be 0.05 degree above the temperature of the protection 
bath. In all experiments, therefore, the temperature of the 
protection bath was adjusted so as to be 0.05 degree below the 
freezing-point of the solution. It was also found with water 
that the protection bath required to be this same amount (0.05 
degree) below the freezing-point in order that the value of the 
freezing-point, with a very small quantity of ice present, might 
agree with that obtained with a large amount of ice. 
The method of carrying out an observation of the freezing- 
point was as follows:—The freezing-tube was filled with the 
solution up to a mark on the glass (about 70 cc.) It was then 
placed in the freezing bath where it remained till the tempera- 
ture was lowered with constant stirring to about 0.5 degree 
below the freezing-point of the solution, this point having been 
determined by a preliminary experiment. The freezing-tubes 
were now quickly removed to the protection bath which was at 
the required temperature (0.05 degree below the freezing-point 
of the solution), and the stirring started. After ten minutes 
time, in which the solution had risen to within 0.1 degree of 
its freezing-point, a small crystal of ice was introduced through 
a glass tube in the cork. As the particles of ice gradually formed 
throughout the solution the mercury in the thermometer rose, 
and in about a minute assumed a fixed position. The tapping was 
begun and continued for half a minute when both it and the 
stirring were stopped, the microscope brought into position and 
a reading made. After again stirring and tapping, the ther- 
mometer was read again, this readiag acting as a check upon 
the former. Care was taken to keep the protection bath constant 
at the required temperature throughout both these readings. 
The tubes were now removed, the ice melted, and the same 
operation repeated for a second observation. 
