102 CONDUCTIVITY AND VISCOSITY OF SOLUTIONS 



mixture are, of course, not true percentages either by weight or volume. 

 The true percentage, however, is of no consequence so long as the 

 mixture is thus defined. Actually, the mixture of 500 c.c. acetone 

 diluted to 1 liter at 20 contains about 42 per cent by weight of 

 acetone, and the mixture of 250 c.c. of acetone diluted to 1 liter con- 

 tains approximately 20 per cent by weight of acetone. 



SOLUTIONS. 



Solutions of one-tenth normal and all greater concentrations were 

 made by dissolving the requisite weight of salt. The N/50 and N/100 

 solutions were made from the N/10 by dilution; and the N/200 and 

 N/400, respectively, were made from these. The N/800 and N/1600 

 concentrations were prepared in the same manner from the N/200 and 

 N/400. The last two concentrations were thus made in three dilutions 

 from the N/10 concentration. Upon the basis of a probable percentage 

 deviation of 0.10 per cent in the original weight of salt, and in the 

 measurement of the solvent in the flask, and of 0.40 per cent in the 

 measurements from the burettes, the probable errors in the value of V 

 at these greatest dilutions is about 0.70 per cent. The probable error 

 in the other dilutions is, of course, much less than this, being within 0.14 

 per cent in the case of the N/10 and all greater concentrations. 



All solutions were made up at 20. No correction for changed 

 normality at higher temperatures had been applied to the values 

 obtained for molecular conductivity. Rise in temperature, of course, 

 diminishes the normality of a solution. This effect is accompanied by 

 an increase in molecular conductivity which is complex. While this 

 increase in conductivity due to temperature, is of the same order of 

 magnitude as that produced by the same lowering of normality caused 

 by diluting with more of the solvent, the two effects bear no known 

 relation to each other. 



SALTS. 



The rubidium salts used in this work were Kahlbaum's purest pro- 

 ducts. They were recrystallized two or three times from conductivity 

 water, precipitated and washed with alcohol, and dried at 120 to 135 

 according to the nature of the salt. The iodide was pure white after 

 drying, and the more concentrated solutions were only slightly colored 

 after standing several days. 



PROCEDURE. 

 CONDUCTIVITY MEASUREMENTS. 



The values of the molecular conductivity /JL V are computed from the 



VOL 



relation ju c = K r, where v is the number of liters of solvent containing 



a gram-molecular weight of the salt; w, the resistance in ohms; a/6, 

 the ratio from the Wheatstone bridge; and K, the cell constant. 



The cell constants were determined with solutions of potassium 

 chloride of N/50, N/500, and N/200 concentrations. The value taken 



