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XXXVII. 



THE DETERMINATION OF THE VOLATILE FATTY ACIDS BY 

 AN IMPEOVED DISTILLATION METHOD. 



By JOSEPH REILLY, M.A, D.Sc, F.E.C.Sc.L, 



AND t 



WILFEED J. HIOKINBOTTOM. 



[communicated by de. f. e. HACEETT, M.A.] 



(Plate XLIX.) 



Read December 17, 191S ; published April 11, 1919. 



During the course of an investigation of the volatile products obtained in 

 certain fermentation processes, the need arose of identifying and estimating 

 mixtures of the lower members of the fatty acid series. When experiments 

 were carried out employing the various methods or modified methods referred 

 to in the literature, the results obtained from comparative determinations 

 varied considerably. It was then decided to consider the problem of the 

 estimation of the volatile fatty acids as a separate investigation. This 

 problem, owing to its importance in biochemical research, has attracted the 

 attention of many workers. The methods suggested for the estimation of the 

 acids can be classified generally into two broad groups. In the one advantage 

 is taken of the varying solubilities of different salts or of the free acids 

 themselves, while in the other the rate of distillation of the acids or their 

 esters is considered. Variations in solubility between adjacent members of 

 the fatty acid series or corresponding derivatives are, however, usually small, 

 and sharp separations by the solubility method are difficult to obtain. In the 

 present paper the second method only will be considered. 



Separation by distillation depending on the varying rates of distillation 

 of different acids was first suggested by Liebig. 1 He partially neutralised the 

 acid mixture before distillation. This method gives, according to Holzmann, 2 

 fairly approximate results for mixtures of the higher acids, but is unsatis- 

 factory for mixtures such as those of acetic and propionic acids. 



1 Annalen, 1849, 71, 355. 2 Arch. Pharm., 1898, 236, 409. 



SC1ENT. PROC. R.D.S., VOL. XV., NO. XXXVII. 4 L 



