342 ON THE SURFACE TENSION AND 
Comments on above Tables. 
Surface Tension.—The differences between observed and 
calculated values are well within the limits of error, through the 
whole range of the observations used in determining the 
ionization constants ; and in the case of the K,SO, somewhat 
beyond this. The alternation of sign is also satisfactory. 
Specific Gravity —For all the salts examined, and through a 
somewhat greater range of concentration than that of the obser- 
vations used in determining the constants, the differences are 
within the limits of error. Change of sign is also quite satis- 
factory. 
It thus appears that for both properties of all the salts 
examined, the expression under consideration represents the 
observed values well throughout the range to which it has been 
applied. 
Mixtures. 
Tables IV and V contain the results of the endeavor to 
predict the values of the surface tension and specific gravity for 
mixtures by means of the above expression (2) of page 335, 
employing the values of the ionization constants obtained as 
above from observations on simple solutions. All the mixtures 
whose specific gravity I determined, were mixtures of equal 
volumes of the constituent solutions. | Rother’s mixtures were 
mixtures of equal weights, which renders the calculations much 
more tedious. His paper, however, furnishes the requisite data 
for determining the volumes of the solutions which he mixed ; 
and these are given in the table below. As I had equi-molecular 
solutions of the Copper and Potassium Sulphates prepared for 
the purpose of finding their electrical conductivity, these solu- 
tions were used in preparing the mixtures for specific gravity 
measurements. 
The following tables also contain the ionization coefficients 
in the mixtures, as determined by the graphical method reterred 
to above. Concentrations of solutions are expressed in terms of 
equivalent gramme-molecules of anhydrous salt per litre at 
18°C. The specific gravities are those at 18°C, referred to water 
at 18°C. 
