CHAPTER VIII. 



CONDUCTIVITIES, TEMPERATURE COEFFICIENTS OF CONDUCTIVITY, 



AND PERCENTAGE DISSOCIATION OF SOME RATHER 



UNUSUAL SALTS IN AQUEOUS SOLUTION. 



BY CHARLES WATKINS. 



This investigation is a contribution to the study of the conductivity, 

 temperature coefficients of conductivity, and dissociation of electrolytes 

 in aqueous solutions. It is a continuation of the work begun by Jones 

 and West 1 in 1905, and which has been in progress continuously since 

 that time. After studying thirty-two substances, organic and inorganic, 

 with special reference to the effects of temperature over a range of 

 to 35, Jones and West reached the following conclusions : 



1. A large increase in conductivity due to greater ionic mobility 

 accompanies a rise in temperature. 



2. A rise in temperature brings about a slight decrease in dissocia- 

 tion. This is in accord with the law of Dutoit and Aston, connecting 

 the association of a solvent with its dissociating power, and is in har- 

 mony with the results of Ramsey and Shields, showing the relation 

 between the dissociating action of water and rise in temperature. 



3. Temperature coefficients of conductivity expressed in percentage 

 units decrease with rise in temperature. 



4. The temperature coefficients of conductivity expressed in con- 

 ductivity units, in the case of salts, increase with rise in temperature, 

 while in the case of acids they decrease. 



Jones and Jacobson 2 next investigated 35 compounds over the same 

 range of temperature used by West, and found that: 



1. The molecular conductivity of electrolytes in aqueous solutions 

 increase as a parabolic function of the temperature from to 35. 



2. Hydrolysis is a source of error in obtaining the value of ju^. 



3. The conductivity of water is a linear function of the temperature. 



4. Salts strongly hydrated in solution show greater increase in con- 

 ductivity with rise in temperature than salts that are slightly hydrated. 



Aqueous solutions of organic acids were the subject of several inves- 

 tigations by Jones and his co-workers. White, 3 while engaged in this 

 work, found that the percentage temperature coefficients of conduc- 

 tivity of most of the organic acids examined were small, and decreased 

 with rise in temperature and with increase in dilution. The rate of 

 decrease of these coefficients, expressed in conductivity units, with rise 

 in temperature, indicates that these acids are much less hydrated than 

 mineral acids. In the case of the amino acids, the percentage coeffi- 

 cients of conductivity are very large. Internal salt formation was 



1 Amer. Chem. Journ., 34, 357 (1905). *Ibid., 40, 355 (1908). 3 Ibid., 42, 520 (1909). 



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