Carter.] -"^^ [March 20, 1885. 



turer for examination. A specimen of perfectly pure lard oil was obtained 

 and they were subjected to the same tests. 



According to Professor Bechi, of Florence, the following test is re- 

 liable and delicate for detecting cotton seed oil in olive oil. The reagent 

 is a one per cent solution of nitrate of silver in absolute alcohol. Place 

 5 c. c. of the suspected oil in' a glass flask, add to it 25 c. c. of absolute 

 alcohol and 5 c. c. of the test solution of nitrate of silver made as stated 

 above. The flask is heated in a water bath at 84° C. (direct heat must not 

 be used). If there be any cotton seed oil present, the mixture will begin 

 to darken, the most minute quantity serving to discolor, and the tint 

 assumed will depend upon the amount of cotton seed oil present. The test 

 depends upon the fact that cotton seed oil will reduce nitrate of silver, but 

 olive oil will not. This reduction is also caused by rape seed oil, but 

 according to Bechi, pure olive oil will remain without discoloration under 

 this test. "While experimenting with the test I thought it might be of ser- 

 vice in detecting cotton seed oil in lard oil ; accordingly the sample of 

 chemically pure lard oil was treated with absolute alchohol and nitrate of 

 silver as directed and then heated ; there was not the slightest discoloration 

 of the pure lard oil ; even on standing for two weeks it did not darken, 

 thus proving it had no action upon the nitrate of silver. The lard oil 

 obtained from the woolen manufacturer was then tested in the same man- 

 ner ; when it had been heated for a few minutes it began to darken and 

 finally became quite black, thus proving that the lard oil was not pure 

 but mixed with some other oil. I am not certain that the darkening is due 

 to reduction ; having made a series of experiments with salts of mercury, 

 copper, and antimony and cotton seed oil to see if there would be any 

 reduction I obtained no satisfactory results, and no reduction was no- 

 ticed. 



The elaidin test is sometimes very satisfactory, especially in detecting 

 a mixture of a drying and non-drying oil and detecting adulteration 

 of olive oil. This test depends upon the fact that olein and oleic acid 

 in contact with' peroxide of nitrogen yield a crystalline, solid, fatty body 

 fusible at 32° C. to which Boudet has given the name elaidin. The 

 nitrous vapors made by the action of nitric acid on copper are passed 

 through the oil, or it may be shaken with a fresh solution of mercurous 

 nitrate which has the property of retaining nitrous acid. "Non-drying 

 vegetable oils and most animal fats contain oleic acid. The following oils 

 contain a high percentage of olein: olive, almond, rape, arachis (earth- 

 nut), castor and the oils from lard and tallow. These oils form with nitro- 

 gen peroxide solid elaidin of a white or yellow color which in some cases 

 is firm and resonant. The drying oils, such as linseed, hemp seed and 

 poppy seed oils do not form solid elaidin with nitrous vapors but remain 

 liquid for more than two days and become slightly colored. The 

 elaidin test was applied to the adulterated lard oil and to the pure lard oil 

 by adding an equal amount of nitric acid (Sp. Gr. 1.40), and some copper 

 turnings. The elaidin produced by the purp oil was more firm and coher- 



