Conductivities and Viscosities in Formamid. 39 



A survey of the work on the salts of all the alkali metals shows 

 that conductivity values for the caesium, rubidium, and potassium salts 

 are approximately the same, and for sodium and lithium are less. 

 The same relation is true for the results obtained in aqueous solutions. 

 Dissociation percentage is of the same order of magnitude for all the 

 salts named. The conductivity results, in connection with the disso- 

 ciation percentage, harmonize with the ionic velocities. For caesium, 

 rubidium, and potassium the relative ionic velocities are 73.6, 73.5, 

 and 70.6, and for sodium and lithium they are 49.2 and 39.8. 



The most striking difference between these metals is shown by the 

 atomic volume curve of Lothar Meyer. 1 This function increases by 

 nearly regular steps from 12 for lithium to 72 for caesium. In accord- 

 ance with the theory of Jones and Veazey, 2 to which reference has already 

 been made, the percentage increases in the viscosity of the concentrated 

 solutions over the viscosity of the solvent, should be the smallest for 

 caesium salts, and should increase in the following order ; caesium, rubid- 

 ium, potassium, sodium, and lithium. This relation comes out clearly by 

 comparing the figures given in the last column of tables 8 to 27. (Com- 

 pare these results for caesium and rubidium salts with those for sodium 

 and lithium) . The salts of rubidium and caesium increase the viscosity 

 of formamid much less than sodium and lithium salts. The difference 

 in percentages of increase is not so marked as the difference in the 

 atomic volumes of the metal ions. The effect is partially suppressed 

 by other factors. Consider the solution of a binary salt which is 80 

 per cent dissociated. Every hundred molecules of the salt gives, in 

 solution, 80 anions, 80 cations, and 20 molecules. The 80 cations are 

 only 44.5 per cent of the number of particles in the solution. It is 

 only this 44.5 per cent of cations which have the atomic volume rela- 

 tions referred to above. The molecular volumes do not show this 

 relation, and the atomic volumes of the anions is unknown. 



SUMMARY OF RESULTS. 



The first six of the conclusions drawn below have been developed 

 or confirmed by the investigations in this laboratory with other pure 

 solvents, and have been shown by this investigation to hold true for 

 formamid. 



1. The greater the dielectric constant of a solvent the greater its 

 dissociating power. 



2. The greater the association factor of a solvent the greater its 

 dissociating power. 



3. The formation of solvates with formamid is indicated by those salts 

 that form hydrates with water. 



'Lieb. Ann. Suppl., 7, 354 (1870). 



2 Carnegie lust. Wash. Pub. No. 80 (1907); Amer. Chem. Journ., 37, 405 (1907). 



