CONSTANTS FOR IDKNTIFICATION OF FATS AND OILS 245 



types of unsaturated acids. The methods for performing the test, as well 

 as the procedure for the calculation, are described elsewhere. ^''*~^^" 



(.9 ) 1\( ■ icli ( ' rl-A I r isd N u mbc r 



The Reichert-Mei.ssl number is usually defined as the number of milliliters 

 of 0.1 N alkali required to neutralize the soluble volatile fatty acids distilled 

 from Jive grams of fat. In order to give the greatest amount of information, 

 this constant should be considered in connection with the Polenske number, 

 and also in some cases with the Kirschner value. 



The Reichert-Meissl nimiber is of especial \^alue in the characterization 

 of butter fat. This is the only edible fat containing appreciable amounts of 

 \'olatile soluble fatty acids, although coconut oil contains a large proportion 

 of volatile insoluble fatty acids. According to Jensen'^^ the Reichert- 

 Meissl value accounts for 85 to 88% of the butyric acid, 85 to 100% of the 

 caproic acid, and 24 to 25% of the caprylic acid present in butter fat. The 

 total volatile fatty acids in this product amount to 10 to 13.6% of the total 

 acids. The failure to account for the full quota of butyric and caproic 

 acids in the usual determination of the Reichert-Meissl value is to be traced 

 to their incomplete removal by steam distillation. However, if certain 

 arbitrary procedures are followed, comparable results may be obtained, 

 although they do not necessarily give the absolute amounts of the several 

 fractions. The low recovery of caprylic acid results, not only from the 

 fact that all the acid cannot be removed by steam distillation, but also from 

 the very low^ solubility of the acid, w^hich precludes its determination in the 

 Reichert-Meissl estimation. 



Butyric, caproic, and to some extent caprylic acids are thus classed as 

 the volatile fatty acids readily or slightly (caprylic) soluble in water which 

 are included in the Reichert-Meissl figure. On the other hand, caprylic, 

 capric, lauric, and also myristic acids belong in the category of volatile 

 fatty acids w^hich are almost incompletely soluble in water (with the ex- 

 ception of caprylic) and which are the basis of the value referred to as 

 the Polenske number. 



The Reichert-Meissl value of butter shows extreme variations between 

 12 and 40, but the figures for most samples fall between 24 and 34. How- 

 ever, slight variations in technic, such as altering the size of the sample 

 employed, may result in markedly different results. With coconut oil, 



3^« W. H. Irwin, R. W. Bailey, T. C. Law, C. P. Long, H. J. Morrison, M. L. Sheely, 

 L. M. Tolman, H. P. Trevithick, and J. J. VoUertsen, Ind. Eng. Chem., Anal. Ed., 8, 

 233-237 (1936). 



'« Anonymous, J. Assoc. Official Agr. Chem., 21, 87-88 (1938). 



^" G. S. Jamieson, Vegetable Fats and Oils, 2nd ed., Reinhold, New York, 1943, pp. 

 25, 395, 474. 



3^' O. Jensen, Z. Untersuch. Nahr. Genussm., 10, 265-283 (1905). 



