72 



Conductivities and Viscosities in Pure and in Mixed Solvents. 



TABLE 46. Constants. 



SUMMARY. 



A satisfactory radiomicrometer, having a half-period of 10 seconds 

 and a sensibility of 5 per square millimeter of exposed vane (candle and 

 scale being at a meter's distance) was constructed. Making use of the 

 radiomicrometer and the grating spectroscope, a radiometric method 

 was worked out for the determination of the ionization constants of 

 indicators. This method is freer from objections and limitations than 

 any method previously used. It serves as well for a two-colored 

 indicator as for a one-colored indicator. 



Very small concentrations of colored components were determined, 

 and it has been shown that minute concentrations of hydrogen and 

 hydroxyl ions can be quickly and accurately estimated by means of 

 radiometric measurements. 



Satisfactory constants were obtained for the ionization of methyl 

 orange as a base. The value found is 2.1 X 1CT 11 . 



The ionization and hydrolysis constants for phenolphthalein con- 

 sidered as a monobasic acid are far from being satisfactory. 



From the known ionization constant of methyl orange and from 

 radiometric measurements, the ionization constant of a very weak 

 base and the hydrolysis constant of one of its salts have been roughly 

 determined. The method can likewise be applied to the determina- 

 tion of the ionization constants of very weak acids, and the hydrolysis 

 constants of the salts formed by these acids. Work is now in progress 

 in this laboratory on other indicators from this same standpoint. 



