60 Dr. Meyer Wilderman on the Velocity of 



the experimental proof of van't HofFs constant, &c. (Zeit- 

 schrift fur physikalische Chemie, 1894-1896 ; Phil. Mao-. 

 December 1897 ; Proc. Roy. Society, 1896). In the equation 

 for the velocity of cooling of the investigated liquid by the 



surrounding medium -r- = C(t g —t), the value of C was 



0*0032 x 2'3026 min. -1 , the difference between the real and 

 apparent freezing-point was 0°'00002 to 0°*00006 (see Phil. 

 Mag. Dec. 1897, p. 484), and also other sources of error were 

 here avoided, as in the case of the very accurate freezing-point 

 experiments. The velocity with which my mercury-ther- 

 mometer assumed the temperature of the liquid was never- 

 theless only about 20° min." 1 . By this method I investigated 

 the velocity of separation of the solidified solvent from over- 

 cooled liquids or solutions, the velocity of separation of salts 

 from supersaturated solutions, and the velocity of melting of 

 cubes of ice in water and aqueous solutions ; the results of 

 this investigation were published in the Report of tbe British 

 Association, 1896, in Sections J II., IV., and V. Besides 

 this, I investigated the velocity of solidification of overcooled 

 liquids or solutions : (1) cases in which pure solvent separates, 

 and (2) cases in which a solid solution separates. The results 

 of this investigation were published in the same Report, in 

 Sections I. and II., and are here given in a little more detail. 



1. Velocity of Solidification of Overcooled Liquids 

 and Solutions. [Phenol and Solutions of Water in Phenol.) 



The method used was that of Gernez-Moore. In the glass 

 U-tube, however, one of the arms was replaced by a tube of 

 verj^ thin platinum, the diameter of the tube being about 

 5 mm., for reasons which are given below. The tube was 

 filled with the liquid to be investigated, and a small, very 

 sensitive mercurj^-thermometer was immersed in the liquid, 

 enabling the temperature to be read to 0°*1. The U-tube 

 was placed in a tall glass jar containing about 8 litres of water, 

 and the temperature of the water was kept constant to o, 05. 

 The temperature of the water was successively arranged at 

 lower and lower temperatures below that of the freezing-point 

 of the liquid contained in the tube. The time was read to 4 of 

 a second. If the freezing-temperature of the pure liquid or 

 of the solution in the tube be T , the temperature of the bath 

 and of the liquid in the U-tube Tb (read directly on the small 

 thermometer before the reaction of the solidification was 

 started), and the temperature of the liquid in the U-tube 

 during the process of solidification T' (the maximum tern- 



