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 2 S0 4 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. Bother'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 referred 

 to above. Concentrations of solutions are expressed in terms of 

 equivalent gramme-molecules of anhydrous salt per litre at 

 18C. The specific gravities are those at 18C, referred to water 

 atl8C. 



