determine the Stability of IrreversiUe Hydrosols. 121 



The figures in the fourth column are very remarkable. AVhen the 

 particles are electro-negative, equicoagulative solutions of acids agree 

 in their electric conductivity within the limits of experimental error. 

 The same relation is clearly shown if one takes the measurements 

 which Picton and Linder made of the power possessed by acids of 

 coagulating the hydrosol of arsenious sulphide. 



0-001 2950 



Value of K referred Sp. mol. conductivity when 



Acid. to AlgClg as unity. 1 gr. equiv. = 1000 c.c. 

 HBr 

 HI 

 HCl 

 HNO3 



H2SO4 0-0006 1935 



Oxalic 0-0005 578 



H3PO4 0-00007 230 



When, however, the particles are electro-positive, the conductivity 

 of equicoagulative strengths of acids varies to a remarkable extent. 



Acids. : ; W" 



Mastic, electro-negative 12-6 14*4 13-9 



Ferric hydrate, electro-positive 1650 6-8 0*7 



Now specific conductivity (C) has the relation 

 C = noL{u-\-v) 



where a is the fraction of the total number of molecules (n) which are 

 dissociated at any one moment, and u + vis the sum of the velocities of 

 the two ions. The factor u + v plays an important part, as will be 

 seen by comparing the values for nx in equicoagulative solutions of 

 acids with slowly moving ions with those with rapidly moving ions : — ■ 



na. 



H3PO4 0-01 



Acetic acid 0-07 



HCl ^ 



H2SO4 U'004 



HNO3 J 



This, however, is probably partly due to the fact that owing to the 

 manner in which the coagulative power was measured, time has 

 practically a constant small value. The values for n might, perhaps, 

 be different if the duration of the experiments were prolonged indefi- 

 nitely. 



