[ 855 ] 



XXXII. — The Boiling and Freezing Points of Concentrated Aqueous Solutions, and 

 the Question of the Hydration of the Solute. By Rev. S. M. Johnston, 

 B.A., D.Sc, F.R.S.E. (Carnegie Research Fellow, etc.). 



(MS. received March 4, 1907. Read same date. Issued separately September 9, 1907.) 



PART I. 



CONTENTS. 



1. Results of Boiling Point and Freezing Point PA0E 



Observations 856 



2. Results of Conductivity Observations at 99 - 4° 



Centigrade and at 0° Centigrade . . 861 



3. Comparison of Results obtained at High and PAGE 

 Low Temperatures from Several Points of 

 View 865 



4. Hydration Data for the Boiling Point, also 

 for the Freezing Point .... 866 



In this paper the results of observations of the elevation of the boiling point of 

 aqueous solutions of electrolytes are given, and a few results of observations of the 

 depression of the freezing point, together with conductivity data obtained by observa- 

 tions of conductivity at about 99 "4° and 0° Centigrade. 



The methods adopted for the boiling-point experiments and the conductivity 

 experiments at 99*4° were the same as those the details of which I have given in the 

 Trans. Boy. Soc. Edin., vol. xlv. (1), p. 193, 1906. 



The method adopted in the determination of freezing points was to reduce the 

 temperature of the solution (of which from 20 to 30 cubic centimetres were taken), by 

 the use of a Beckmann freezing-point apparatus or through the use of Dewar vacuum 

 tubes, until some ice was formed in the solution. The tube containing the solution was 

 then withdrawn, placed in a bath of about one degree higher temperature than its 

 freezing point, and the ice allowed to almost disappear. The temperatures of the 

 formation and the disappearance of the ice were noted. When the ice had disappeared 

 the experiment was repeated, the temperature of the freezing bath being kept about one 

 degree below the freezing point of the solution. When ice appeared in the solution, 

 the solution was again removed to the bath of slightly higher temperature than its 

 freezing point, and the ice allowed to disappear. The temperatures of formation and 

 disappearance of ice were noted and their mean taken, which was looked upon as the 

 freezing point of the solution. Had the object of this research been a thorough 

 investigation of dilute solutions from the freezing-point point of view, an effort after 

 greater delicacy of method would have been made. My object, however, was quite 

 different, namely, that a few comparisons might be made of results obtained from the 

 freezing-point method for the more concentrated solutions with those obtained from the 

 boiling-point method, and only a very few determinations of freezing points have been 

 made for the dilute solutions. The freezing mixtures used were, for the Beckmann 

 apparatus, ice and calcium chloride (crystallised) or ice and sodium chloride ; for the 



TRANS. ROY. SOC. EDIN., VOL. XLV. PART IV. (NO. 32). 124 



