LARD AND LARD ADULTERATIONS. 465 



To avoid the disturbing effect of the chloroform iii the above process 

 Mr. A. H. Allen recommends the use of the fat acids for absorbing 

 iodine instead of the natural glycerides. 



(d) Reaction with nitrate of silver. * The solutions used have been of 

 two kinds, viz: (a) one-fifteenth to one-tenth gram of Ag NO 3 in 200cc 

 of 95 alcohol and 20cc ether. 



Of this solution lOcc should be taken for each test. (&) One gram 

 Ag ISTOs in 200cc of equal parts of alcohol and ether. Of this solution 

 Ice was used. The mixture of 85 parts of amyl alcohol and 15 parts 

 of rape-seed oil was the same in both cases, lOcc of the mixture being 

 used in each test. The method of making the test has also been changed. 

 I use a porcelain dish 8 to 10cm in diameter. The re-agents with the 

 oil (lOcc) are thoroughly mixed by shaking in a test tube and then poured 

 into the dish and placed on a steam bath. The contents of the dish are 

 occasionally stirred and the heating is continued for twenty minutes. 

 The deposition of silver on the dish is easily seen and the resulting col- 

 ors show more clearly on the white porcelain. 



Solution (b) acts more promptly than (a), but the results with (a) are 

 more satisfactory. 



The order of the phenomena will be found to be as follows: 



For pure cotton oils. In from two minutes to three minutes the mixt- 

 ure turns red. In five to ten minutes the red color becomes so brown 

 as to appear black, in thick layers. At the end of the test metallic sti- 

 ver is deposited on the sides of the dish varying in color from bluish black 

 to reddish purple. The liquid carries also particles of reduced silver 

 and has a decided greenish tint. 



With lards containing more than 20 per cent, of cotton oil the phe- 

 nomena observed above are repeated, but not so promptly. 



Even with very small percentages of cotton oil, the characteristic re- 

 actions are given. 



Animal fats give no color, under similar treatment, or at most a faint 

 red after twenty minutes. 



Of vegetable oils I have examined rape seed, olive, peanut, and lin- 

 seed. These act with the re agent like the aDimal fats. 



One hundred samples of lard and twenty-five samples of cotton oil have 

 been examined by Bechi's test. In no case, where cotton-seed oil has 

 been present, has the test failed in detecting it, except in two doubtful 

 cases of alleged cotton oil to be mentioned further on. 



Of the 100 samples of lard examined 74 were found to be adulterated 

 with cotton oil. 



SOME PECULIAR REACTIONS. 



The reaction with crude cotton oil is not as sharp as with the refined 

 oil. The deep red color of the sample seems to obscure the final color 

 reactions. 

 Linseed oil gave a reddish color but no reduction of silver. In three 



* Journal of Analytical Chemistry, Vol, 2, part 3, July, 1888. 

 17319 pt. 4 5 



