452 Transactions. — Chemistry and Physics. 



Art. LVI. — The Molecular Complexity of the Fatty Acids 

 and their Derivatives in Phenol Solution. 



By P. W. Bobertson, Sir George Grey Scholar, Victoria 



College. 



Communicated by Professor Easterfield. 



[Read before the Wellington Philosophical Society, 18th March, 1903.] 



Plates XLVIII. and XLIX. 



Phenol, in spite of certain drawbacks, is a popular solvent 

 for the determination of the molecular weight of compounds 

 by the well-known Baoult's method. Not only is it cheap 

 and easy to obtain in a pure state, but it also has a con- 

 venient melting-point (41°). Further, it has a large molecular 

 depression, and the magnitude of this quantity increases the 

 accuracy of the determinations. Indeed, Easterfield and 

 Bee* have shown that results of the required accuracy can be 

 obtained by the use of a common thermometer and a test- 

 tube. 



At the proposal of Professor Easterfield I examined the 

 association of water in phenol solution. From this I set 

 about examining other compounds ; my experiments with 

 the fatty acids I propose to describe in the following com- 

 munication. 



First, however, I shall consider shortly the main points 

 in the history of the cryoscopy of phenol. Baoult in his 

 historical researches gave the value of the molecular depres- 

 sion as 67"5. In 1890 Eykman altered the value to 72. 

 With a view to clearing up this apparent discrepancy, Juil- 

 lard and Curchodf investigated the question, and came to the 

 conclusion that the compound has two distinct values, 76 and 

 68 - o, for the so-called constant. The reason of this is not far 

 to seek, for the value 68 was obtained for associating com- 

 pounds — e.g., water, alcohols, and acids — while the higher 

 number resulted when substances known to be normal were 

 employed. The experiments below, however, show that even 

 for one class of organic compounds the results for the value of 

 the molecular in dilute solution (when the freezing-point is 

 depressed 1°) vary from 82 to 64 — i.e., nearly 25 per cent. 



* Trans. N.Z. Inst., 1901, 497. 

 t Bull. Soc. Chim. [3] 6, 237. 



