BY MIXTURES OF ELECTROLYTES BARNES. 141 



of molecules and ions present seems to affect the power which 

 one molecule or ion has of lowering the freezing-point, it was 

 assumed that the depression produced by a molecule or an 

 ion of say, the electrolyte 1, which is surrounded by mole- 

 cules and ions of this electrolyte 1 and of the other electro- 

 lytes 2, 3, etc., would have the same value as if all the molecules 

 and ions surrounding it were of electrolyte 1. Thus the M's 

 of the above expression have been regarded as equal to the 

 molecular depressions in simple solutions of the concentration 



N i+ N 2 + etc - 



The application of this expression to the calculation of the 

 depression in mixtures will form at once a test of the above 

 assumption and a test of the ionization coefficients employed. 

 I have applied it (a) to mixtures of potassium chloride and 

 sodium chloride, these salts being selected because of their 

 simple molecular structure and the approximate equality in their 

 grade of ionization ; (b) to mixtures of sodium chloride and 

 hydrochloric acid, selected because of their simple molecular 

 structure and the considerable difference in their grade of 

 ionization ; (c) to mixtures of potassium chloride, sodium 

 chloride and hydrochloric acid, selected for testing in addition 

 the method of finding the ionization coefficients in a mixture of 

 three electrolytes. 



The following is a synopsis of the work involved : Purifica- 

 tion of materials ; construction and calibration of the instru- 

 ments used in the conductivity and freezing-point observations ; 

 preparation and analysis of a series of simple solutions of the 

 three electrolytes ; determination of the specific molecular 

 conductivities at infinite dilution for 0C. ; observations on the 

 conductivity at for the series of simple solutions; calcula- 

 tion of the ionization coefficients at from the conductivity 

 observations ; measurement of the depression of the freezing- 

 point of the simple solutions; calculation of the molecular 

 depression for each solution of the three electrolytes ; prepara- 

 tion of mixtures of two and of the three electrolytes ; measure- 

 ment of the depression of the freezing-point of the mixtures ; 



