ELECTROLYTIC DISSOCIATION 69 



Evidently, then, dissolved salts, strong acids and bases, 

 must he treated with caution as electrolytes, for though 

 there is undoubtedly dissociation, and the assumption of 

 dissociation into ions appears to be indispensable, yet the 

 exact amount of that dissociation, and the mechanism of it, 

 are insufficiently explained. In these cases it is necessary 

 to hold by the thermo-dyiiamic relations based on vapour 

 and osmotic pressures, &c., and to treat the calculations 

 made from conductivity data as rough estimates, whose 

 exact value is yet to be determined, although the commonly 

 close agreement indicates a most valuable conclusion, as 

 will appear better in the Third Part. 



It is otherwise as regards high dilutions, at which, 

 especially for strong monobasic acids, monacid bases, and 

 their salts, the dissociation found osmotically and electrically 

 is practically complete, and so ignorance of the law of 

 dissociation does not stand in the way ; calculations then, 

 with the assumption of complete dissociation, recover strict 

 applicability. 



To give a motion of the case, we quote the degrees of 

 dissociation found for decinormal solutions at 1 8 from 

 conductivity measurements : 



Strong monobasic acids and monacid bases : 



HCl 94% KOH 93% NaOH 90% 



Salts of the above acids and bases : 



KCl 86% KN0 3 85% NaCl 84% NaN0 3 84% 



Salts of strong dibasic acids or diacid bases : 



Na 2 SO, 69% BaCl 2 7 5% 



Salts of dibasic acids and diacid bases : 



MgS0 4 45% CuSO, 39% 



Already in the copper salt we are dealing with a weak 

 base ; if further a weak acid be chosen, as in copper acetate, 

 the ionization is further reduced ; then, however, quite 

 a different dissociation appears the hydrolytic which 

 results in formation of free acetic acid and free base or 

 basic salt, an effect that does not come into consideration 

 with the salts mentioned above. 



