MORSE AND PIERCE. — SUPERSATDRATION IN GELATINE. 637 



from which the value of a that most nearly satisfies equation (12) is seen 

 to be 1.80. 



... -^ = ,.80 

 a = 4.25 X 10-^ 



The corresponding value A of the integral is .009668. 

 Therefore from equation (11) 



11=^ 



75 



TT 



(.009668)2 ^ 16 y^ iQ-6 



/Gm. Mol.y 

 \ liter J 



The diffusion constant is not «, but a^ which, reduced to the usual 

 units with the day as unit of time by multiplying a^ by 8.64 X 10^ 

 becomes 



. «— CD- 



In this calculation of H the reacting substances have been assumed to 

 be completely dissociated. The result of the calculation shows that the 

 concentration of the silver ion was about ^^^ Normal and that of the 

 chroraate ion ^i- Normal when precipitation occurred. The dissociation 

 of ry^g silvcr ultrate differs so little from that of ^g^, which enters into 

 the calculation of subsequent cases, that the assumption of its complete 

 dissociation introduces no appreciable inaccuracy. On the other hand, 

 the dissociation of y^ij potassium chromate is about 1.05 times the dis- 

 sociation of jY, ) ^"'^ ^^^^^ factor representing the ratio of dissociation must 

 be introduced into calculations involving different concentrations of potas- 

 sium chromate in the gelatine. 



Observing this precaution we obtain the following values for a'- and // 

 from other sets of data of Table III. 



