ASPECTS OF ADSORPTION PHENOMENA 181 



Conductivity in Conductivity in 



No. of extract gemmhos No. of extract gemmhos 



1 109+ 7 23-25 



2 475-5 8 18-25 



3 2 3 2 '3 9 *5'94 



4 120-4 ... 10 I 5'45 



5 62-8 ... ii !5'4 



6 2 9'4 T 



We sec at once that after a certain time each further change of 

 water contracts only an infinitesimal amount of electrolytes. Since the 

 conductivity of the distilled water was 5 gemmhos, this must be sub- 

 tracted from the values given in the table, leaving only 10 gemmhos 

 for the electrolytes washed out from the gelatin. These electrolytes 

 consist in all probability chiefly of calcium sulphate, and a calcium 

 sulphate solution of 0-25 per cent, has a conductivity of 2039 gemmhos, 

 so that, neglecting differences of dissociation, a solution with a con- 

 ductivity of 10 gemmhos will contain only 0*25 x ~~ = 0-0013 per 

 cent. It may be said that at this stage the ash was nearly all washed 

 out. In order to test this possibility, I determined the ash of the 

 gelatin. The incineration was performed in a platinum capsule, care 

 being taken not to let the temperature get above dull redness, and not 

 to prolong the heating after all charred portions had lost their black- 

 ness. The original gelatin contained 0*55 per cent, of ash, and after 

 extracting with water eleven times it still contained 0^036 per cent. 

 Therefore, when the rate of extraction, had already become almost 

 negligible, there was still left in the gelatin a considerable amount 

 of ash. 



On the hypothesis that the electrolytes are merely mixed 

 with the gelatin and washed out by diffusion, the rate of diminution 

 of conductivity of the successive extracts would have been much 

 greater. This can be seen by calculating on the basis of the amount 

 washed out by the first and second extractions, what would have been, 

 e.g., the conductivity at the seventh extraction. The proportion 

 removed at each change would, obviously, have been the same. If 

 the above calculation be made it will be found that the conductivity 

 of extract No. 7 would have been 7-4 gemmhos instead of 23-25 

 gemmhos as found, 



