BY MIXTURES OF ELECTROLYTES. BARNES. 147 



bath kept constantly at 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 0.3 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 hath 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 reading 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. 



