EXAMINATION OF OILS. 53 



l.DIBLE OILS. 



DETECTION OF COTTON-SEED OIL. 



With the exception of cotton-seed oil, the adulterants ordinarily used 

 with edible oils are of such a nature that the experience and training 

 of a chemist and the facilities of a chemical laboratory are essential to 

 their detection. There is, however, a simple test for the detection of 

 cot ton-seed oil, known as the Halphen test, which may be readily 

 applied. 



The reader is cautioned that great care must be taken in the manipu- 

 lat ion of this test, as one of the reagents employed carbon bisulphid 

 is very inflammable. The manipulator should use every possible safe- 

 guard and should see to it that only a small portion of his reagent is 

 exposed at one time. The chemicals emplo3 r ed in the preparation of 

 the reagent used for this test are not household articles. They may, 

 however, be obtained in any pharmacy. The mixture should be pre- 

 pared by a druggist rather than by an inexperienced person who desires 

 to use it. 



In order to perform the test 2 or 3 tablespoonfuls of this reagent 

 are mixed in a bottle with an equal volume of the suspected sample of 

 oil and heated in a vessel of boiling salt solution (prepared by dissolv- 

 ing 1 tablespoonf ul of salt in a pint of water) for ten or fifteen minutes. 

 At the end of that time, if even a small percentage of cotton-seed oil 

 be present, the mixture will be of a distinct reddish color, and if the 

 sample consists largely or entirely of cotton-seed oil, the color will be 

 deep red. 



EGGS. 



There is no better method for the testing of the freshness of an egg 

 than the familiar one of "candling," which has long been practiced by 

 dealers. The room is darkened and the egg held between the eye and 

 a light; the presence of dark spots indicates that the egg is not per- 

 fectly fresh, one that is fresh presenting a homogeneous, translucent 

 appearance. Moreover, there is found in the larger end of a fresh 

 egg, between the shell and the lining membrane, a small air cell which, 

 of course, is distinctly transparent. In an egg which is not perfectly 

 fresh this space is filled and hence presents the same appearance as 

 the rest of the egg. 



It is now a matter of considerable importance to be able to distin- 

 guNh between fresh eggs and those that have been packed for a consid- 

 erable time. Until recently that was not a difficult matter. All of 

 the solutions that were formerly used extensively for that purpose 

 gave the shell a smooth, glistening appearance which is not found in 

 the fresh egg. This characteristic, however, is of less value now than 



See Caution, p. 42. 



