790 



THE MECHANISM OF AGGLUTINATION 



PRECIPITATION BY NON-ELECTROLYTES AND THE MUTUAL PRE- 

 CIPITATION OF OPPOSITELY CHARGED COLLOIDS 



It was noted by Linder and Picton' that two oppositely charged suspensions 

 would precipitate each other if they were mixed in proper proportion. If either com- 



TABLE II 



Cataphoretic Charge and Stability of Suspensions of Particles of 



Collodion 



Suspended in Solution of; 



Minimum Concentration 

 Required for Precipitation 



p.D. m 

 Millivolts 



Maximal Concentration 



at Which Suspension 



Remains Stable 



p.D. m 

 Millivolts 



LiCl 



NaCl 



KCl 



Na2S04 



Na4Fe(CN)6 



MgCL, 



MgS04 



CaCU 



LaCla 



NaCl 



Na2S04 . . . . 

 Na4Fe(CN)6 

 CaClz 



NaCl 



Na2S04 



CaCl. 



LaCls 



H2SO4 



M/2 



m/4 



m/i6 



M/32 



M/2 

 M/4 

 M/32 

 M/2, 04 



m/4 



PH5.8 



pH II. o 



16 

 IS 



m/4 

 m/8 

 M/32 

 M/64 



PH3.0 



7 

 12 

 16 

 14 



m/4 



M/8 



M/64 

 m/4, 096 



M/8 



18 



20 



24 

 19 



14 



(Lost) 

 19 



14 



ponent were present in excess, the suspension again became stable. These observa- 

 tions have since been extended and confirmed for a large number of substances. 



Webster^ has shown that this is also true in the case of mixtures of suspensions of 

 bacteria under such conditions that one suspension was negative and the other posi- 

 tive. It is possible that this phenomenon is connected with the so-called "autoagglu- 

 tinable" bacteria and may at times interfere with agglutination reactions. Thomas^ 



' Picton, H., and Linder, S. E.: J. Chcni. Soc, 61, 148. 1892; 67, 63, 1895; 71, 568. 1897; 87, 

 1906. 1905. 



^Webster, L.: J. General Physiol., 7, 513. 1925. 



3 Thomas, A. W., in Bogue, R. H.: Colloidal Behavior, i, 324. McGraw-Hill Book Co., 1924. 



