Conductivities and Viscosities in Formamid. 



35 



lectric constant, association factors, and viscosities of the solvents. 1 

 Reference to table 7 (p. 24) shows that formamid is a solvent markedly 

 different from any other pure solvent investigated in regard to the three 

 constants mentioned. The evidence obtained supports and confirms 

 all the relations and conclusions that have been established by Jones 

 and his co-workers, from their investigations with other pure solvents. 

 These relations will be discussed in turn. 



The Thomson 2 -Nernst 3 theory is that the forces which hold the atoms 

 together are electrical; hence the solvent having the highest dielectric 

 constant has the greatest dissociating power. The dissociating power 

 of solvents is shown in two ways: first, by comparing the percentage 

 dissociation of solutions having the same normality ; second, by com- 

 paring the dilutions at which complete dissociation is reached. Com- 

 pare table 12 with table 28. 



TABLE 28. Potassium Iodide in Water. 



Table 12 shows that the dissociation of the N/2 solution of potassium 

 iodide in formamid is only 71 per cent at 25. From the viscosity data 

 in table 12, we calculate that the viscosity of the N/2 solution is 12.4 

 per cent greater than the solvent, while the viscosity of the N/2 solution 

 of potassium iodide in water is known to be less than that of the solvent. 

 From a large mass of evidence, we know that viscosity is by far the 

 largest factor affecting conductivity in solutions in which dissociation is 

 of the same order of magnitude. The conductivity of the N /2 solution in 

 formamid at 25 is 18.67. We can assume, without appreciable error, 

 that if the viscosity of the solvent and the N/2 solution were in the same 

 ratio as in the case of the potassium iodide solution in water, the conduc- 

 tivity of the N/2 solution in formamid would be at least 12.4 per cent 

 larger than the figure given 18.67. Recalculating the dissociation of 

 the potassium iodide-formamid solution on this basis gives 79.4 per cent, 

 compared with 76.6 per cent for the potassium iodide solution in water. 

 This latter figure would be even less, if corrections were made for the 

 fact that the viscosity of an N/2 solution in water is less than that of 

 the solvent, which would be a legitimate correction to make for the 

 purpose of this comparison. Comparing in this way the dissociation 

 of these two N/2 solutions, we find, as would be expected from the 

 Thomson-Nernst theory, that formamid has the greater dissociating power. 



results have been tabulated and discussed in publications of the Carnegie Institution of 

 Washington, Nos. 170, 180, and 210. 



2 !>hil. Mag., 36, 320 (1893). 3 Zeit. phys. C'hem., 13, 531 (1894). 



