86 Messrs. Hinshelwood and Hartley on the Probability of 

 This must be equal to A ; 



.-. J(U„-/3T*)=- or r = 2 



pr _ P (U -/3T 2 )J- 



a is not known precisely ; but since for the small tempe- 

 rature differences of a few degrees with which we are 

 concerned we may regard it as constant, the variation of r. 



is chiefly governed by ^ -^ 2 . 



From the melting-point of p.-tolnidine, 43°* 3, and its 

 latent heat of fusion, 39 cals. per gram, U and /3 are 

 calculated in the usual way ; whence 



_2a 1 



r ~ p (19-5--000195T 2 )J cm '' 



where J - Mech. Equiv. of Heat. 



This allows us to calculate the following values of r, which 

 are plotted against temperature in fig. 3 : — 



Variation with temperature of radius of particle 

 in equilibrium with liquid. 



Temp. r. 



2(7 



35° C 0-24xlO-7X— cm. 



P 



30 0-15 



25 0-11 



20 0-086 



15 0-072 



(b) Fig. 2 gives the number of tubes of para-toluidine out 

 of the 122 used, which crystallized instantaneously at different 

 temperatures. The points are numbered in the order in which 

 the measurements were made, to illustrate the comparative 

 absence of progressive changes in activity. We now suppose 

 that those tubes in which crystallization occurred instanta- 

 neously contain active particles of radius equal to or greater 

 than the equilibrium radius for this temperature, and thus 

 by eliminating the temperature between curves 2 and 3 we 

 obtain the distribution of particles of various radii among 

 the tubes. Curve 4 gives the number of tubes containing 

 active particles with radii greater than a certain limit. 



