WORK OF P. B. DAVIS. 



197 



solutions of the various rubidium salts and of ammonium iodide at 25 to 45. It 

 is evident that of the halogen salts of rubidium the iodide produces the greatest 

 change in fluidity, followed by the bromide, then the chloride. This may be ex- 

 plained by the fact that when the cation, here rubidium, to which the increase in 

 fluidity is mainly due, remains the same, the negative viscosity effect is a function 

 of the molecular volumes of the salt in question. 



If we divide the molecular weights of the three halogen salts by their densities 

 referred to water as a unit, we obtain the following values : 



Rbl, 



212.37 

 3.02 



= 7.02; RbBr, 



165.37 



2.78 



5.95; RbCl,-^- =5.496. 



35 



x 



o 



3 



o 

 O 



a 



30 



I 25 



x 



'3 



E 



20 



15 



11.3 2 4 10 



Volume Concentration 

 Fig. 84. Conductivity and Fluidity of Rubidium Iodide in Glycerol at 25. 



Reference to table 142 will show that the experimental data are in accord with 

 this; rubidium iodide at 25 producing a per cent increase in fluidity of 26.3, rubi- 

 dium bromide 18.5, and rubidium chloride 12.2. It was impossible to prepare a 

 normal solution of rubidium nitrate in glycerol at the temperature 20. The N/2 

 solution was nearly saturated at that temperature, and shows somewhat greater 

 negative viscosity coefficients than would be expected. 



The N/4 solution, however, gives values between that of rubidium bromide and 

 iodide, which is to be expected from its molecular volume. No adequate explana- 

 tion can be offered for the apparently abnormal negative viscosity coefficients of 

 ammonium iodide in glycerol. 



In table 143 is given the percentage increase in fluidity at 25 produced by the 

 two salts showing the most marked negative viscosity effect, viz, rubidium iodide 



