184 PROPERTIES OF ELECTRICALLY CONDUCTING SYSTEMS 



In the following table are given values for the conductance of picric 

 acid in methyl alcohol in the presence of water. 9 



TABLE LXXI. 



CONDUCTANCE OF PICRIC ACID IN CH 3 OH AT 25 IN THE 

 PRESENCE OF WATER. 



Concentration of Water Cone. 



.5 1. 2. of Acid 



9.32 12.7 16.3 23.4 0.1 

 56.73 63.7 70.2 75.7 0.0015625 



In this case, the conductance effect due to addition of water is the reverse 

 of that in solutions of stronger acids. The conductance increases 

 throughout as the concentration of water increases. It is evident that 

 the ionization of picric acid is much smaller than that of the stronger 

 acids. The increase in the conductance at the higher concentration is 

 much more marked than it is at the lower concentration, indicating that 

 at higher concentration, at least, an increase in the ionization due to the 

 addition of water is a primary factor in causing an increase in the con- 

 ductance of the solution. It may be presumed that the speed of the 

 hydrogen ion is independent of the nature of the acid, and that conse- 

 quently the A values for picric acid decrease with increasing amounts 

 of water, until fairly high concentrations are reached. In the following 

 table are given approximate values of A for picric acid dissolved in 

 methyl alcohol in the presence of water. 10 



TABLE LXXII. 



CHANGE OF A FOR PICRIC ACID IN METHYL ALCOHOL WITH VARYING 

 AMOUNTS OF WATER. 



C H20 .5 1. 2. 



A 182 108 98 90 



These values of A , while only approximate, nevertheless cannot differ 

 greatly from the true values and clearly indicate that the increase in 

 the conductance of picric acid is due to an increased ionization of the 

 acid as a result of the presence of water. 



In solutions of weaker acids, the effect of water on the ionization of 

 the acid is even more pronounced. In the following table are given 

 values for trichlorobutyric acid: 11 



Goldschmidt and Thuesen, loc. cit. f p. 35 

 10 Ibid., loc. tit. 

 n /6id., loc. cit. f p. 37. 



