68 



FOODS AND FOOD ADULTERANTS. 



acids from genuine butter fat rarely exceed 83 per cent., occasionally reaching 89 

 per cent., but a sample ought scarcely to be regarded as certainly adulterated unless 

 the insoluble acids exceed 89J per cent. As a standard for calculation 88 per cent, 

 of insoluble acids' may be regarded as a fair average, the soluble acids being taken 

 at f> per cent. 



Allen, in a later contribution to the literature of Eeichert's method, 

 says: 2 



A further experience in the employment of Reichert's process for examining fats 

 has led me to abandon the expression of the results in terms of butyric acid, in favor 

 of a statement of the weight of caustic potash neutralized by the distillation from 

 100 grams of the oil. This is obtainable by multiplying the volume of decinormal al- 

 kali neutralized by the distillate from 2.5 grams by the factor 0.2244. 3 



The following table contains a number of results expressed in both ways : 



From these results it is evident that the fats of different kinds of milk (butter fats) are 

 sharply distinguished from nearly all other fats by the large proportion of soluble vola- 

 tile fatty acids they yield by Reichert's process. The most remarkable exception is 

 presented by porpoise oil and some samples of whale oil. In porpoise oil I have found 

 5 per cent, of valeric acid, and Chevreul obtained as much as 9.63 per cent. In a re- 

 cent paper I pointed out that in porpoise butter the glyceride of valeric acid appeared 

 to replace the butyrin characteristic of the butter of terrestrial mammals. 



Some of the chemists who have employed Reichert's process take the precaution to 

 filter the distillate before titrating it, so as to get rid of any volatile acids which may 

 be insoluble or very sparingly soluble in water. This plan may sometimes be adopted 

 with great advantage. Thus when the solution of the soap obtained by saponifying 

 cocoanut or palm-nut oil is acidulated and distilled, a notable proportion of lauric 

 acid passes over and solidifies in the condenser or on the surface of the distillate ; and 



^The percentage of adulterant in a butter fat may be calculated from the following 

 formula, in which F. is the percentage of foreign fat and 1 that of the insoluble fatty 

 acids: F= (1-88) X 13.3. Or each 0.1 per cent, of soluble acids above 0.5 may be re- 

 garded as showing the presence of 2 per cent, of butter fat. 



2 Analyst, 1887, pp. 11 et seq. 



3 1 cc. of 



alkali contains 0.00561 grain of KOH; and 005 ^ 1 r Xl0 = .2244 



2.*> 



