Role of Salts in Peesbrvation of Life 185 

 TABLE V 



CoefScient of Antago- 

 nization KCl/CaOl. 



LI c.c. m/2 KCl in 100 c.c. H^O require . 1 m/100 CaCU .... 550 

 1.65 c.c. m/2 KCl in 100 c.c. H.O require 0.5 m/lOO CaCl.. . . .165 



2.2 c.c. m/2 KCl in 100 c.c. H.O require . 3 m/100 CaCL .... 366 

 2.75 c.c. m/2 KCl in 100 c.c. H.O require 1.0 m/100 CaCl.. .. .137.5 



3 . 3 c.c. m/2 KCl in 100 c.c. H^O require 1 . 6 m/100 CaCU .... 103 



The coefficients are not as regular as in the case of antagoni- 

 zation of KCl by NaCl. This is due to the fact that the minimal 

 value of CaClj at which it renders the KCl harmless cannot 

 be determined as sharply as the limit for NaCl. Why is less 

 CaCl2 required than NaCl ? We can only answer with a sug- 

 gestion first offered by T. B. Robertson, namely, that CaCl2 

 produces its protective effect through the formation of a com- 

 paratively insoluble compound (in this case On the gills or the 

 rest of the surface of the animal) while NaCl acts through the 

 formation of a compound which is more soluble. This view 

 is corroborated by the observation which we made, that Sr is 

 just as effective to antagonize KCl as CaClj, but that Mg 

 is much less efficient. This would correspond with the well- 

 known fact that many strontiimi salts are just as insoluble, if 

 not more insoluble, than the calcium salts, while the magnesium 

 salts are often incomparably more soluble, for instance, in the 

 case of the sulphates. BaCl2 antagonizes KCl also powerfully, 

 but, probably, in consequence of the fact that the substances 

 formed at the surface of the animal or the gills, diffuse slowly 

 into the cells, the fish do not remain alive as long if Ba is used as 

 if the more harmless Ca and Sr are used. 



It is very remarkable that CaClj renders harmless any given 

 concentration of KCl below 6.6 c.c. m/2 KCl in 100 c.c. of the 

 solution, but not above this limit. This limit is exactly the 

 same which we found in the case of antagonization of KCl by 

 NaCl. Even the combination of NaCl and CaClg does not 

 permit us to render harmless more than 6.6 c.c. m/2 KCl in 

 100 c.c. of the solution. 



