CHEMICAL AGENTS ON CHROMATOPHORES 



157 



ber of gram equivalents in cms. is the molecular conductivity' 

 of the substance written as A- However, the conductivity is at 

 its maximum at infinitely dilute solutions, therefore the value 

 A°° is taken as a measure of the total number of ions that are 

 produced by the dissociation of one gram equivalent of the 

 substance. Therefore d the degree of dissociation is directly 

 proportional to the conductivity; thus we have the simple form- 



\ 



The equivalent conductivity at infinite dilution 



ula a = 



A 



for KCl is calculated to be 130.10. The equivalent conductivity 



of a two-tenth molecular KCl is 107.96 A 0.2 m. The degree of 



A 0.2 M 107.96 

 dissociation at 18°C. is the ratio —. , or -.57777, or 82.98 



7\. cc loO.lO 



per cent. The values obtained in this way may be regarded 

 only as approximate. The values are given in the following 

 table. 



TABLE 1 



A study of the table leads one to believe that the rate and the 

 degree of the contraction are in some way correlated with the 

 degree of dissociation of the salts. The lowest rate and degree of 

 contraction was found in K2SO4, where the degree of dissociation 

 is 66.03 per cent. The most rapid and complete contraction 

 occurred in KI where the dissociation is 84.82 per cent. 



Potassium nitrate is out of place. It has a greater stimulating 

 action than its degree of dissociation would indicate. It should 

 fall between potassium sulphate and potassium chloride. The 

 possible explanation for this break in the series may be that the 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 23, NO. 1 



