FAT CRYSTALS l6l 



Drown zone which deepens to wine red. The reaction for sperm 

 oil is much as for cod-liver oil. These color reactions with sul- 

 phuric acid are perhaps of little value in the detection of fat adul- 

 terations and admixtures but they will prove helpful aids in the 

 examination of these substances as to identity. Pure concen- 

 trated acid should be used. It must also be kept in mind that the 

 at impurities which may be present modify the color reactions. 

 Pure samples of fats should be kept on hand for purposes of making 

 check and comparative tests. The Bureau of Animal Industry 

 las suggested a method for distinguishing between fats and oils 

 derived from the animal and the vegetable kingdoms based upon 

 differences in the appearance of the crystals (phytosterol and 

 cholesterol). 



In addition to the study of fat crystals which are formed spon- 

 aneously in more or less decomposed and aged meat products as 

 above set forth, certain methods for testing fat crystals isolated 

 n the pure state by chemical methods are now generally carried 

 out in meat inspection and food laboratories. These tests corn- 

 Dine the use of the compound microscope and should therefore 

 )e carried out by the micro-analyst or bacteriologist and for that 

 eason are hereby included. R. H. Kerr of the Biochemic Divi- 

 ion of the Bureau of Animal Industry has worked out a method 

 or detecting vegetable fats in mixtures of animal and vegetable 

 ats and vice versa, the method will also serve to demonstrate the 

 presence of animal fats in supposedly pure vegetable fats. The 

 nethod is a slight modification of several methods which have been 

 n use for some time and which are described in various text-books, 

 and it is hereby given in full as it appears in Circular No. 212 (May 

 10, 1913) of the Bureau of Animal Industry. 



THE DETECTION OF PHYTOSTEROL IN MIXTURES OF ANIMAL AND 



VEGETABLE FATS 



Sample. The amount of sample used depends on the amount of material avail- 

 able. From 200 to 300 grams is the amount usually taken. The test is seldom 



