124 COLLOID CHEMISTRY OF THE PROTEINS 



Hence, on the widely accepted assumption * that the degree of 

 dissociation of equivalent solutions of alkali globulin is the 

 same : 



//. = a (u Na + v Glob .) and p' = a (w NH4 -f u G iob.) 

 and therefore : 



At 18, )Lt N H 4 /*Na = 20, and from this the values of a and v G iob. 

 given in the table are deduced. A value for the absolute 

 mobility of the negative globulin ion of at least 777 X io~ 5 

 cm./sec. is thus obtained. 



Hardy has determined the mobility of the globulin ion 

 directly, using Whethan's method, in which the displacement 

 of the bounding surface between the liquid under investigation 

 and another of equal conductivity lying above it, on applying 

 a known difference of potential is measured. The value of 

 911-5 x io- 5 cm./sec. was found in solutions of globulin 

 chloride, and for sodium globulinate 7-66 X io~ 5 cm./sec. for the 

 mobility of the globulin ions. The latter value for the negative 

 globulin ion is in excellent agreement with that which we have 

 obtained from the conductivity. Acid globulin, particularly 

 that formed with weaker acids, permits of the variation of the 

 degree of dispersion of the globulin solution by addition of the 

 acid in stages. On account of the hydrolysis which occurs, the 

 size of the disperse particles can be varied over the wide range 

 between a slight opacity and a thick precipitate. Hardy's 

 work on globulin acetate shows that the electrophoretic 

 behaviour is independent of the size of the globulin particles, 

 which agrees with observations made on all kinds of colloids. 

 It is well known that colloidal solutions as a rule contain 

 disperse particles of varied size, as the production of colloids 

 * Discussed in the section on alkali caseinates, pp. 101 109. 



