CHEMICAL AGENTS ON CHROMATOPHORES 



159 



a metal and any solution of its salts, but rather the difference 

 in pressure between a single ion and a single atom of the metal 

 that determines the chemical action of the ions. Since solution 

 tension is a measure of the difference in potential between the 

 solution which contains a known amount of the ions of the metal 

 and the metal itself, it is also the difference between the tendency 

 of an atom of the plate to become an ion. When applied to 

 living protoplasm the metal plate is replaced by the protoplasm. 

 The value varies with the amount of electrolytic dissociation 

 and the kind of plate present. 



The solution tensions in volts of elements in normal ionic 

 solutions. 



Cl 1.694 



K 2.92 Br 1.270 



Na 2.54 1 0.797 



NO3 2.229 



The ionic potential is the reciprocal of the solution tension. 

 Ionic potential is the tendency of any ion in any concentration 

 of solution to change into an atom of its metal. 



The ionic potentials of the ions of metals in volts are: 



Cl 1.694 (?) 



K 2.92 (?) Br 1.270 (?) 



Na 2.54 (?) 1 0.797 (?) 



NO3 2.229 (?) 



Mathews ('06) shows that the dissolving power of the salts 

 of sodium and potassiun for edestine, a globulin of the hemp 

 seed is in some way correlated with the ionic potential. 



