ALUMINIUM HYDEOXIDE BY ELECTROLYTES. 



25 



When the concentration is large enough, even electrolytes 

 with the weakest coagulative power can cause considerable increase 

 in the relative viscosity as is illustrated by the following ob- 

 servations on nitric acid. 



TABLE 14. 



But when the concentration of an electrolyte is so large, the 

 viscosity is generally increased to some extent even without 

 coagulation taking place. Hence it will be necessary to apply 

 proper correction to obtain more exact results. In the present 

 investigation we have limited ourselves to the study of more 

 dilute solutions. 



Although it seemed highly improbable that positive ions 

 should exercise any considerable coagulative powTr on the col- 

 loidal aluminium hydroxide, we studied the effect of the nitrates 

 of the following six cations, 



Na, Ag, Ba, Co, Ni, UO,, 



in order to reach experimental certainty on the subject. Up to 

 the concentration of ^ equivalent normal the results were quite 

 negative. Thus we are naturally led to the conclusion that it 

 is anions which cause the coagulation. 



The fact, that succinic, maleic, and itaconic acid are quite 

 inactive up to the highest concentration tested, while their sodium 

 salts exercise considerable coagulative power even in tolerably 

 dilute solutions, is in accordance with this conclusion. But the 



