134 



CONDUCTIVITY AND VISCOSITY 



ammonium bromide, rubidium iodide, and rubidium bromide in each 

 of the solvents. Figure 53 shows the conductivity curves of ammonium 

 iodide in the ternary solvents at 25 degrees, and figure 54 shows the 

 corresponding fluidity curves. While these curves have the same 

 general character, some marked differences are noticeable. The fluidi- 

 ties of glycerol, water, and acetone at 25 degrees are respectively 0.17, 

 112.30, and 288.95. The values for glycerol and water are taken from 

 the data of Jones and Davis and those for acetone from the work of 

 Jones and Bingham. A study of these two figures in the light of 

 the Thompson^Nernst 2 , and Dutoit- Aston 3 hypotheses will afford an 

 explanation of all cases of non-parallelism in the two sets of curves. 

 Since reducing the association of the solvent affects both its fluidity 

 and dissociation, and since the relative effect on each is not known, 

 the above explanation is to be regarded as only qualitative. 



40 



30 



8 20 



10 







2-1-1 2-2-1 2-1-2 1-1-1 1-2-1 1-1-2 1-2-2 - Solvents 



FIG. 53. Conductivity of ammonium iodide in glycerol, acetone, and water, at 25. 



As an illustration, consider the change from the 1-1-1 solvent to the 

 1-2-1. The fluidity increases 5 times as much as the conductivity. 

 The changes affecting fluidity are as follows : the water changes from 

 33 to 25 per cent causing a small reduction; glycerol changes from 

 33 to 25 per cent causing a rather large increase, while acetone changes 

 from 33 to 50 per cent, causing a very large increase. The changes in 

 water and glycerol would each reduce the conductivity, while the 

 change in acetone would increase the conductivity much less than the 

 fluidity. A consideration of the above details makes it clear that a 

 much larger increase in fluidity than in conductivity should be expected. 



Other changes from one solvent to another can be explained by 

 similar considerations. Thus, figures 55 and 56 show fluidity and 

 molecular conductivity curves for rubidium bromide in the 1-2-1 and 

 the 1-1-2 solvents at 15, 25, and 35. Jones, Davis, and Hughes 

 have shown that for glycerol-water mixtures and acetone-water mix- 

 tures, temperature coefficients for fluidity are larger than for con- 

 ductivity, because rising temperature decreases the dissociation. 



'Phil. Mag., 36, 320. (1893.) 2 Zeit. phys Chem., 13, 531. (1894.) 



3 Compt. Rend., 125, 240. (1897.) 



