84: Messrs. Hinshelwood and Hartley on the Probability of 



formed in which the molecules are orientated. If the radius 

 of the particle is equal to or greater than that of the particles 

 of solid which would be in equilibrium with the liquid at. the 

 temperature of the experiment, then the nucleus will grow 

 and crystallization will take place immediately. But if the 

 radius of the dust particle is smaller than this equilibrium 

 radius, then crystallization will not take place until, as the 

 result of: a series of fortunate chances, the nucleus has been 

 built up to the necessary size. The average time which 

 must elapse before this happens obviously depends upon the 

 discrepancy between the radii of the largest active dust 

 particles present and the radius of the nucleus which is first 

 capable of continued growth. 



The Influence of Temperature. 



The curve in tig. 1, which refers to p. -tol incline, and the 

 numbers in Tables III. and IV. show that as the temperature 

 is lowered, the number of crystallizations taking place almost 

 instantaneously increases largely, but that the remainder of 

 the curve resembles exactly some portion of a curve for a 

 higher temperature. 



The radius of the particles in equilibrium with the liquid 

 diminishes with temperature. Hence, some of the dust 

 particles too small to effect immediate crystallization at 

 one temperature maybe able to do so at a lower temperature.. 

 As the temperature falls the average life of each tube 

 diminishes, and some reach a critical temperature at which 

 crystallization takes place at once. This is in a sense a 

 compromise between the views of Ostwald and de Coppet. 



The dependence of average life upon size of particle 

 present. 



The attempt to determine this is rendered more difficult 

 by the gradually changing degree of dispersion of the 

 colloidal particles throughout a series of experiments. 



Madinaveitia and Aguirreche * and Rocasolano -f- have 

 shown that as a platinum sol ages and its degree of 

 dispersion diminishes, its catalytic activity first increases 

 slightly and then decreases. A precisely similar effect is 

 found in the formation of crystal nuclei, but only rarely 

 is there an initial increase. It is found that with diphenyl- 

 amine the tendency to crystallize at first increases and then 

 falls otf — the increase being due probably to the initial 



* Anal. Fis. Qurm. xix. p. J24 (1921). 

 t Anal, Fis. Quim. xix. p. 1U (1921). • 



