ASPECTS OF ADSORPTION PHENOMENA 209 



congo-red to electrolytes is also shown by the curves ; even at the 



low concentration of ^- of the electrolyte they do not fall to the 



oooo J J 



level of the amount taken up from the particular sample of water used, 

 which amount is represented by the horizontal line with an ordinate 

 value of 20 per cent. It is noticeable, on the contrary, that the 

 curves tend to become asymptotes. I am not prepared to give any 

 interpretation of the form of these curves. 



V. CONDITIONS OF DISSOCIATION OF ADSORPTION COMPOUNDS 



" ---**- ** t f 



Recent research has brought to light the important part played in 

 vital phenomena by the mutual relations of colloids to electrolytes and 

 to other colloids. Since these relations are apparently those of 

 adsorption, it is of some importance to know- what are the conditions 

 under which this association is broken down. 



1 . Temperature 



We have already seen that dissociation is favoured by rise oi 

 temperature, and that, on the other hand, if suddenly exposed to the 

 temperature of boiling water, a dyed piece of paper becomes to a 

 certain degree fixed in its condition, so that the dye can only with 

 difficulty be extracted by water. 



2. Precipitation 



It was noticed by Cramer and Swale Vincent 1 that the inorganic 

 constituents of various organic bodies are set free when these bodies are 

 acted upon by precipitants of bases. I have observed the same fact in 

 the case of the precipitation of gelatin by tannin. 



Experiment: 'A 15 per cent, solution of gelatin had a specific 

 conductivity of 1570 gemmhos at 38-5. 20 c.c. of this solution were 

 mixed with 90 c.c. water and 10 c.c. of 10 per cent, tannin solution, 

 filtered, and 100 c.c. filtrate concentrated to 20 c.c. The conductivity 

 of this was now 2750 gemmhos. This 20 c.c. would represent J 2 

 of the first, so that the conductivity should be multiplied by ' 

 3300 gemmhos, that is, the conductivity was doubled by the action of 



I. Journ. of Physiology, XXX, p. 150, 1903. 



