. JOHN H. NORTHROP 



119 



reached is independent of the size of the particles and therefore of 

 their surface. These experiments were repeated under sKghtly dif- 

 ferent conditions several times — always with the same result. This 

 would indicate that the process is either one of solution, in which 



TABLE III. 



Removal of Pepsin from Solution by Dif event Substances. 



10 cc. of pepsin solution, pH 2.5, + 0.5 gm. of substances noted. Allowed to 

 stand 10 min. at 25°C. and pepsin estimated in 1 cc. of solution. 



Substance. 



Control; pepsin solution alone 



Starch 



CaS04 



Agar 



Kaolin 



Blood charcoal 



Casein 



" (coagulated, dried, and ground to 40 mesh) 



" (extracted with boiling alcohol for 24 hrs.) 



" C (charred at 150°C.) 



Egg albumin (coagulated, dried with acetone, and finely powdered) 



Relative 



quantity of 



pepsin per 



cc. 



100 

 98 

 86 

 103 

 100 

 15 

 70 

 74 

 60 

 90 

 10 



TABLE IV. 

 Efect of Size of Particles of Egg Albumin, Coagulated, Dried, and Ground. 



2.0 gm. in 20 cc. of pepsin solution titrated to pH 2.5 + HCl. 

 1.0 cc. pipetted oflf and analyzed for pepsin at time noted. 



