1428 FOODS AND FOOD ADULTERANTS. 



Resin oil has a polarization of from +30 to +40 on the sugar 

 scale (Schmidt and Haensch) in a 200 mm tube, while other oils read 

 between +1 and 1. 



HALPHEN a REACTION FOR COTTON-SEED OIL. 



Carbon disulphid, containing about 1 per cent of sulphur in solu- 

 tion, is mixed with an equal volume of amyl alcohol. Mix equal vol- 

 umes of this reagent and the oil under examination and heat in a bath 

 of boiling brine for fifteen minutes. If no red or orange tint is pro- 

 duced, 1 cc more of reagent is added and the mixture again heated for 

 fifteen minutes. The presence of 1 per cent of cotton-seed oil will be 

 shown by this treatment. 



At the same time it must be remembered that lard and lard oil from 

 animals fed on cotton-seed meal will give a faint reaction; also the 

 fatty acids from the same. 



This test is more sensitive than the Bechi test and less liable to give 

 unsatisfactory results in the hands of an unexperienced person. It is not 

 affected by rancidity. The depth of color is proportional, to a certain 

 extent, to the amount of oil present, and by making comparative tests 

 with cotton seed some idea as to the amount present can be obtained, 

 but it must be remembered that different oils react with different 

 intensities, and oils which have been heated to 200 to 210 react with 

 greatly diminished intensity. 1 * Heating ten minutes at 250 renders 

 cotton-seed oil incapable of giving the Halphen reaction. 



BECHI OR SILVER NITRATE TEST FOR COTTON-SEED OIL. 



Reagent. , d Dissolve 2 grams of silver nitrate in 200 cc of 95 per 

 cent alcohol and 40 cc of ether, adding 1 drop of nitric acid. 



Mix 10 cc of oil or melted fat, 5 cc of reagent, and 10 cc of amyl 

 alcohol 6 in a test tube. Divide, heat one-half in a boiling water bath 

 for ten minutes, and then compare with portion not heated. Any 

 blackening due to reduced silver shows presence of cotton -seed oil. 



Other oils which have become rancid/ and lards which have been 

 steamed or heated at high temperature, contain decomposition prod- 



a G. Halphen, Jour. Pharm. Chim., 1897, (>, 390-391; Analyst, 1897, 22, 326; 

 Allen, Com. Org. Anal., 3d ed., vol. 2, pt. 1, p. 143; Winton, Conn. Exp. Sta. 

 Kept, 1900, pt. 2, p. 144. 



b Allen, Com. Org. Anal., 3d ed., vol. 2, pt. 1, p. 143. 



Holde and R. Pelgry, Jour. Soc. Chern., Ind., 1899, 18, 711. 



d Pearman and Moor, Allen, Com. Org. Anal., 3d ed., vol. 2, pt. 1, p. 143. Wesson, 

 Jour. Am. Chem. Soc., 1895, 17, 724. 



e The addition of amyl alcohol is not necessary, but the writer finds it very con- 

 venient, as it dissolves the oils or fats and enables one to mix the oil and reagent 

 much better. 



f Wesson Jour. Am. Chem. Soc., 1895, 17, 724; A. L. Winton, Conn. Expt. Sta. 

 Kept., 1900, pt. 2, p. 143. 



