CONDUCTIVITY OF COLLOIDAL MIXTURES 



313 



Fenn's hypothesis as stated above does not explain why every 

 salt should not increase penneability. However, in a second 

 paper' he describes further experunents and states their appli- 

 cation to protoplasm. To explain the decrease in penneability 

 caused by CaClo he postulates a condition of protoplasm in which 

 there is a predominance of anions. This may be brought about 

 in gelatine by the addition of a small amount of NaOH, which 

 belongs to the third group of electrolytes and antagonizes both 

 NaCl and CaCL. The gelatine plus NaOH bears a negative 



Fig. 7 



charge because of the greater adsorption of the sodium ions. 

 When either NaCl or CaCL are added antagonism occurs but not 

 at the same molecular proportions, for calcium ion is much more 

 readily adsorbed than the sodium ion. The latter even at low 

 concentrations are numerous enough to overcome the OH ions 

 and transform the charge of the gelatine to the positive side of 

 the isoelectric point. The Ca ions on the other hand are 

 actively adsorbed and those that remain are not numerous 



' Fenn, W. O. Similarity in the Behaviour of Protoplasm and Gelatine. 

 Proc. Natl. Acad. Sci. 2: 539. 1910. 



