80 Messrs. Hifishelwood and Hartley on the Probability of 



The catalytic nature of the process of nucleus formation. 



The study of the phenomenon is complicated from the 

 outset by the fact that the formation of a nucleus is a 

 catalytic process. 



Previous observers have stated that the tendency of a 

 supercooled liquid to crystallize depends upon the tempe- 

 rature to which it has been previously heated *, on the 

 number of times fusion and solidification have taken placet, 

 and on the length of time it has been maintained in the 

 fused state %. 



These influences were very evident in our first series 

 of experiments, which were made with salol contained in 

 steamed-out soda-glass tubes 5 cm. x 0*8 cm. Equal volumes 

 (about 2 c.c.) of salol were placed in all the tubes, which 

 were numbered so that an individual record of each might 

 be kept. The results are given in Table I. (see p. 92). 



With seventy tubes fairly smooth curves were obtained for 

 the relation between time and number of crystallizations. 



Fig. 1. — Spontaneous crystallization of Para-toluidine. 



Mfnyte$ 



This justifies the application of the laws of probability 

 to the results. The form of the curves is explained in the 

 next section. (The salol results are not plotted here, but 

 the similar series with p.-toluidine is shown in fig. 1.) 



* de Coppet (loc. cit.). 



f Karl Schaum, Zeitschr. pfajs. Chem. xxv. p. 722 (1898). 



\ Ibid. 



