60 



CONDUCTIVITIES AND DISSOCIATIONS 



dilutions that a change in the dilution would change the coefficients 

 very slightly. 



The temperature coefficients of conductivity of acids, even of mineral 

 acids to a certain extent, decrease with rise in temperature. The 

 literature shows also that the mineral acids are more or less hydrated 

 in solution. It is evident that an acid which is either unhydrated or 

 only slightly hydrated (as is the case with most of the organic acids 

 studied in this investigation) would show a rapid decrease in the 

 temperature coefficients of conductivity with rise in temperature; 

 since there would be no complex hy- 

 drated ion to lose water, and, thus, 

 from this cause, the conductivity 

 could not be increased. This point 

 is illustrated in table 19, which gives 

 the temperature coefficients of certain 

 weak, unhydrated acids at F=1024. 



Table 20 from the work of Jones 



TABLE 19. 



and Wightman, 1 gives similar values for some of the hydrated acids; 

 two weaker acids racemic and citric show the same decrease in 

 the coefficients as the strong acids. This indicates that the strength 

 of the acid has very little to do with the gradual decrease in 

 temperature coefficients, but that this decrease is caused by hydra- 

 tion; and the above relation applies to the strong acids only because 

 they are the acids which are the most strongly hydrated. This same 



TABLE 20. 



relation holds in this work. The temperature coefficients of conduc- 

 tivity of the acids are larger for stronger acids. This is shown by 

 table 21, in which the acids are arranged according to their strengths. 

 All the work done in the Chemical Laboratory of the Johns Hop- 

 kins University on the conductivity of organic acids has shown that 

 the temperature coefficients of conductivity expressed in percentage 

 decrease slightly with increasing dilution and more rapidly with rise 

 in temperature. The decrease due to rise in temperature manifests 



. Chem. Journ., 46, 56 (1911). 



