192 ELECTRIFICATION OF WATER 



into beakers containing solutions of acid the level of the pure water in 

 the flask rose during the first 20 minutes or more whenever the concen- 

 tration of the acid was m/256 and the rise increased with an increase 

 in the concentration until the concentration was about m/4. Then 

 the level of the water inside the flask fell again. 



In the presence of acids water diffuses through the membrane in the 

 form of negatively charged particles. We have assumed that the 

 drop is due to the repelHng action of that ion of the electrolyte which 

 has the same charge as the water particles; i.e., the anion in the case 

 of acids. Our assumption is supported by the fact that aside from 

 the degree of electrolytic dissociation the drop increases with the in- 

 crease of valency of the anion of the acid as we should expect. The 

 drop is least in the case of the acids with monovalent anion (NO3 

 and CI), is greater in the case of SO4 and oxalate anion, and still greater 

 in the case of PO4. The drop in citric acid is a Httle less than in oxaKc 

 acid, as is to be expected from the fact that citric acid is a weak acid. 

 In the case of acetic acid no rise and drop in the curve is noticeable 

 except the rise due to the gas pressure effect of the solution. 



In the case of alkaHes we are restricted to low concentrations by the 

 fact that they dissolve the collodion membranes when the concen- 

 tration becomes moderately strong. As Fig. 12 shows, we observe 

 absolute negative osmosis in the case of Ca(0H)2 and Ba(0H)2 when 

 the concentration of the solution exceeds m/256. In the case of alka- 

 lies with monovalent cation the usual drop in the curves — i.e. relative 

 negative osmosis — was observed, but not an absolute negative osmo- 

 sis; i.e., an absolute diminution of the volume of the solution. 



The negative osmosis in the case of acids and alkahes becomes abso- 

 lute for the reason that the initial rise in the curve due to the attrac- 

 tive action of the ion with the opposite sign of charge from that of 

 the water is too sHght or entirely lacking in the case of the acids or 

 alkaHes. 



The writer was interested in finding out whether aluminium salts 

 with bivalent or trivalent anion induce negative osmosis. In Fig. 

 13 are plotted the curves representing the influence of different con- 

 centrations of AI2CI6, Al2(S04)3, and aluminium citrate on the rate of 

 diffusion of water through a collodion membrane. All the solutions 

 had about the same hydrogen ion concentration and the water diffused 



