( 193 ) 



VIII. — On the Elevation of the Boiling Points of Aqueous Solutions of Electrolytes. 



By Rev. S. M. Johnston, D.Sc. 



(MS. received 8th February 1906. Read 19th February 1906. Issued separately, 11th July 1906.) 

 (The expense of this research was partly covered by granls from the Moray Endowment and the Carnegie Trust.) 



CONTENTS. 



PAGE j PAGE 



Part I. Part III. 



An Improvement in the Method of Determining j Conductivity Measurements at the Boiling Point. 



Elevation 193 An i mprove( j Method. Instruments sketched 208 



Part II. 

 Determination of the so-called Boiling- Point Con- ART 



stant and Molecular Weight Determinations . 203 I Concentrated Solutions. Hydration. . . . 219 



PAET I. 

 An Improved Method of Determining Elevation. 



It has been known for a length of time that the presence of a non-volatile substance 

 diminishes the vapour pressure of the solvent in which it is placed, and as the boiling 

 point of a solvent or a solution is the temperature at which the vapour pressure is just 

 equal to, or overcomes the pressure of the atmosphere, it follows that a solution has a 

 higher boiling point than the solvent. Amongst the first experimenters in this field 

 were Faraday,* LEGRAND,t Griffiths,} and Raoult.§ To Eaotjlt we owe much for 

 his development of the subject. 



Perhaps from the experimental point of view the subject owes more to Beckmann|| 

 than any other. Not only do we owe to him the very delicate thermometer used in 

 boiling-point work, but also the experimental method whereby determinations may be 

 made. He submitted the apparatus designed by himself to the German Society of 

 Scientists, September 1889, and shortly afterwards published a description of it. Since 

 then his apparatus has undergone several modifications. IF In the various forms of 

 boiling-point instruments which have been designed, one might trace the difficulties 

 which gather around research of this kind. 



* Ann. Chim. Phys., 20, 324. t Ann. Ghim. Phys., 59, 423. 



X Pogg. Ann., 2,. 227. § Compt. Rend., 103, 1125. 



|| Ztschr. phys. Chemie, 3, 603 (1889), 4, 532 (1889). IT Ztschr. phys. Chtmie, 21, 245 (1896), 15, 656 (1894). 



TRANS. ROY. SOC. EDIN., VOL. XLV. PART I. (NO. 8). 27 



