88 



Dr. W. M. Bayliss. 



[Apr. 7, 



charge of the paper has been neutralised or reversed by the cations of a salt 

 in the solution. Or, to put it in another way, the surface energy of the 

 negative paper will not be reduced by the deposition of a body with a further 

 charge of the same sign, whereas this will happen when the two charges have 

 opposite signs. The adsorption of electro-positive colloids by paper is 

 retarded by neutral salts, because they reverse the difference in sign between 

 the two bodies, making it similar, instead of opposite. 



The enzyme experiments were made in the following way : — Equal 

 quantities of the various adsorbents were allowed to remain in contact with 

 solutions of trypsin (2 per cent.) either in distilled water or in 0-018 molar 

 solution of calcium sulphate for 18 hours. They were then filtered off, and 

 equal amounts of each filtrate (2 c.c.) added to equal amounts (20 c.c.) of 

 5-per-cent. ammonium caseinogenate and then incubated at 37° C. for 

 4*5 hours. The relative change was measured by determinations of the 

 electrical conductivity. The results were as follows : — 



Soluble starch 



Charcoal 



Filter paper . 

 Charcoal (2) . 



Water 



Calcium sulphate. 



Water 



Calcium sulphate. 



Water 



Calcium sulphate. 



Water 



Calcium sulphate, 



Water 



Calcium sulphate. 



In reading this table it must be remembered that a larger change means 

 more enzyme in filtrate or less adsorbed. 



The sign of the electric charge on all the bodies used was found to be 

 negative, so that the result of all the experiments, with the exception of 

 those with charcoal, corresponded to what happens when an electro-negative 

 colloid, trypsin in this case, is adsorbed by an electro -negative surface in the 

 presence or absence of neutral salts. In the presence of calcium sulphate 

 more enzyme was taken up by the surface, and therefore the filtrate was less 

 active. The opposite effect of bone charcoal is not easy to explain. It 

 perhaps lies in the circumstance that charcoal contains a certain amount of 

 salts (ash constituents) already, so that, even in the absence of added 

 electrolyte, sufficient was present to ensure maximal adsorption. The 

 slightly greater effect of the filtrate to which calcium sulphate had originally 

 been added would then be explained by the action of the small amount of 



