SURFACE TENSION OF AQUEOUS SOLUTIONS. BARNES. 65 



From Table VII it seems that the specific gravity of solutions 

 of these salts between the concentration of about 0.01 and 0.5 

 can be calculated by aid of the formula and with the values of 

 k and I given, while for surface tension (Table VIII) the calcula- 

 tion seems possible from a concentration of 0.2 to 1.0. 



Mixtures of Solutions. 



For a solution containing two salts, the equation for the 

 value of a property, if there is no change of volume on mixing, 

 is of the form 



v i ' V 2 



where the ris are the concentrations of the constituent solutions, 

 the as the ionization coefficients of the respective electrolytes 

 in the mixture, and the -y's the volumes of the constituent solu- 

 tions, the electrolytes being indicated by 1 and 2. 



The ionization coefficients of the salts in the mixture are 

 obtained by the before-mentioned graphical method from the 

 same curves as were used in the conductivity determinations for 

 mixtures of solutions of these salts. The k's and I's are the 

 ionization constants obtained for the simple solutions, and given 

 in Tables VII and VIII. 



For the specific gravity measurements, equal volumes of the 

 constituent solutions were mixed ; while Rother mixed equal 

 weights of the simple solutions. He, however, gives sufficient 

 data for the calculation of the concentration and volume of the 

 constituent solutions. 



The following table contains the requisite data for deter- 

 mining the values of the two properties from the above equa- 

 tion, and also, for the comparison of the results thus calculated 

 with the observed values. The volumes of the constituent 

 solutions in Table X, are expressed in litres at 18C. The 

 concentrations are expressed as in the former tables. 



PROC. & TRANS. N. S. INST. Sci., VOL. X. TRANS. E. 



