Modification of Beckmann's Boiling Method 



of determining Molecular Weights of 



Substances in Solution. 



by 



Jöji Sakurai, F. C. S. 



Professor of Cliemistry, Imperial University. 



JVith Plate I. 



Recent investigations in Physical Chemistry have extended our 

 means of determining molecular weights of substances. Besides the 

 ordinary method, which depends upon the determination of the 

 specific gravity of a substance in the gaseous state — the so-called 

 " vapour density " method — we have now, thanks to the labours of 

 Kaoult and others, various means of ascertaining molecular weights of 

 substances in solution. Diminution of vapour tension, lowering of 

 the freezing point and rise of the boiling point, of a solvent, are the 

 changes which accompany the dissolution of a solid body in it, and 

 each of these changes supplies us with a means of determining the 

 molecular weight of the dissolved body. These are mutually 

 connected together by theoretical considerations, but for purposes of 

 determining molecular weights the method, which depends upon the 

 change in the boiling point, fnv surjxasses the others on account of the 

 simplicity of the manipulation and of the greater exactness in the 

 results obtained. To lîeckmann (Zeitsch. pkysik. Chan., 3 603 

 [1889] J 4, b'62 [1880J; 5, 76 [1890]; 6, 4H7 [L890]; 8, 223 

 [1891]) we owe the application of this method for laboratory pur- 

 poses; but, in spite of his indefatigaljle labours, there are some points 



