gelatin had soaked, viz., 13*5 c.c. It did not, however, entirely go 

 into solution ; yet notwithstanding this, the conductivity was 29 

 gemmhos as compared with the 10 gemmhos of the water in which the 

 gelatin had been soaked. The signification of this fact is that it con- 

 firms the deduction drawn from the previous experiment that electro- 

 lytes are held by the gelatin in such a manner that they can only be 

 separated by an enormous number of changes of water. 



If gelatin which has been washed free from the greater part of its 

 electrolytes be placed in a dilute potassium chloride solu-tion, it takes 

 up a certain quantity of this electrolyte, which can be washed out by 

 repeated changes of water, and the curve of the conductivities of the 

 series of extracts is of exactly the same form as that of Fig. 2. 



The fact mentioned in the last paragraph makes it of interest to 

 see whether direct evidence can be obtained of the adsorption of 

 electrolytes by gelatin. This can be done in the following way : 



Experiment : 30 c.c. of KQ were found to possess a conductivity 

 of 16,600 gemmhos at 39-7 C. At room temperature 2-3 grams of 

 ' washed ' gelatin were placed therein and allowed to remain for 24 

 hours. The conductivity of the solution was now found to be dimin- 

 ished to 14,590 gemmhos at 39*7. This means that at least 12 per 

 cent, of the potassium chloride had been taken out of solution. 



The fact can also be shown in other ways though in not so 

 obvious a manner. If we take distilled water and add successively 

 equal amounts of KCI, each increment produces a slightly less increase of 

 conductivity than the previous one. The reason is that as the solution 

 becomes more concentrated the KCI becomes less dissociated ; to & 

 less degree also increased ionic friction will contribute to the result. 



o 



If, on the other hand, we add to the water first some 5 per cent, or so 

 of gelatin and afterwards the successive doses of KCI the result is 

 different. In a particular experiment 10 grams of gelatin were placed 

 in 200 c.c. of distilled water, the gelatin having been previously washed 

 fairly free from electrolytes. The conductivity of the water was raised 



to 26*9 gemmhos. When 2 c.c. KCI were added and allowed to 

 stand for 24 hours the conductivity was increased by 200 gemmhos. 



