PROTOPLASMIC STRUCTURE 91 



dyes on adsorbing surfaces in an insoluble fomi and the 

 ^'denaturation" of proteins on surfaces are apparently 

 phenomena of the same general kind; ads(jrption will 

 promote hydrolysis or other chemical alteration in a 

 compound if any reaction-product is more readily 

 adsorbed than the original compound. From this 

 point of view the general kinetics of adsorption-catalysis 

 appear in a clearer light. 



The heavy metal ions and the ions of trivalent 

 metals appear to be adsorbed with especial readiness in 

 many cases, and the solutions of their salts have a corre- 

 spondingly great influence on the surface charge of col- 

 loidal particles and of porous partitions. In the case of 

 suspended oil drops, ElHs^ found the following concen- 

 trations of three chlorides to be equally effective in 

 removing the charge; i.e., in rendering the particles 

 electrically neutral. 



■K/r ^ T •* Relative 



Mols.pcrLitre Concentration 



AICI3 0.00026 I 



CuCla 0.00S9 ca. 40 



NaCl 0.40 ca. 1600 



The relative actions of Na, Cu, and Al are approxi- 

 mately as I to 40 to 1,600, indicating a rapid increase 

 of action with increase of valence. The same rule is 

 found in the precipitation of suspensoid colloids by 

 electrolytes (rule of Schulze and Hardy), and indicates 



^Ridsdale Ellis, Z. physik. Chem., LXXVIII (1912), 321- I^^b's 

 recent study of the effects of ions in altering the charge on suspended 

 collodion particles gives a sunilar result (/. Gen. Physiol., V [1922J, 109). 

 In this case the collodion particles undergo precipitition when the P.D. 

 against the medium falls below 16 millivolts. Bacteria are agglutinated 

 at 15 millivolts accordmg to Northrop and de Kruif (loc. cit.). 



