466 FOODS AND FOOD ADULTERANTS. 



samples of lard made by us from the leaf, guts, and head, respectively, 

 of the same hog, the re-agent acted in the same way. There was a 

 slightly greater coloration with the head and gut lard than with the leaf. 



In samples of " prime steam lard " passed by the Chicago Board of 

 Trade and made from the trimmings of the whole animal, not presum- 

 ably including the leaf, there-agent gave, after twenty minutes, a slight 

 brownish red color, but no appreciable reduction. 



In the whole number of examinations made there were three or four 

 cases in which the results appeared doubtful. A slight reduction of 

 the silver was observed and a color approaching a brown-black, but not 

 with sufficient positiveness to prove the presence of cotton oil. These 

 I have included under the adulterated samples. 



In general, it may be said that any degree of adulteration of laid with 

 cotton oil which would prove commercially profitable is at once detected 

 with certainty by Bechi's test. 



On the oiher hand very impure lards containing no cotton oil will 

 give color reactions and a trace of reduction of metallic silver with 

 Bechi's re-agents similar but not identical witli a trace of cotton oil. 



The reaction is undoubtedly the most valuable single test . for cotton 

 oil which has been proposed. 



It remains to be seen what reactions lard which is made from swine 

 fattened on mast or cotton meal will give with these re-agents. The 

 nature of the reducing agent has not yet been determined. It has been 

 suggested that it is an aldehyde. It appears to withstand sapouifica- 

 tion, and Milliau has lately proposed to use the test on the free, fatty 

 acids of cotton oil. 



Since cotton oil is sometimes refined with alkaline substances, and 

 thus retains an alkaline reaction, it may happen in the application of 

 the above test that a sufficient amount of alkali is present to reduce 

 the nitrate of silver to oxide. In such a case the proper reaction of the 

 cotton oil may be wholly obscured. To avoid this it is best to make 

 the solution of nitrate of silver distinctly acid by the addition of a 

 small quantity of pure nitric acid. 



MILLIAU'S METHOD OF APPLYING THE NITRATE OF SILVER TEST. 



The method of Milliau differs from that of Bechi in applying the 

 solution of silver nitrate to the fat acids instead of to the original glyc- 

 erides. The sapouificatiou may be made in any of the usual ways. 

 About 5cc of the fat acids are sufficient for making the test, which is 

 carried on in a test tube 12cc in length and Sec in diameter. To the 

 acid are added 20cc of strong alcohol and heat applied until the fat 

 acids are dissolved. Add 2cc of a silver nitrate solution containing 

 30 grams of silver nitrate in lOOcc of water; licat in steam bath 

 until about one-third of the alcohol is evaporated. At the end of thi.s 

 time, if the samples bo cotton oil or contain cotton oil the silver will be 

 reduced to a inotalliq state, producing a browu or black color in the 



