EDIBLE OILS AND FATS. 33 



diminished intensity. Heating ten minutes at 250 renders cotton-seed oil incapable 

 of giving reaction. a 



17. BECHI OR SILVER NITRATE TEST FOR COTTON-SEED OIL. b 



Reagent. c Dissolve 2 grains 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 ainyl alcohol d in a test 

 tube. Divide, heat one-half in a boiling water bath for ten minutes, and then com- 

 pare 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 products which have a reducing 

 action on silver nitrate. The writer found in testing a large number of salad oils 

 some which contained no cotton-seed oil, according to the Halphen test, but gave a 

 brown coloration with Bechi reagent, and in some cases reduced silver. These same 

 oils on being purified gave no reaction. Hence the oils or fats should be purified 

 before testing. 



To purify the oils and fats, heat from 20 to 80 grains on water bath for a few min- 

 utes with the addition of 25 cc of 95 per cent alcohol, f shake thoroughly, decant as 

 much of the alcohol as possible, and wash with 2 percent nitric acid, g and finally 

 with water. The oil or lard thus purified will give no reduction at all if it contains 

 no cotton-seed oil. Heating the oils or fats to 100 C. or simple washing with '2 per- 

 cent nitric acid is not sullicient except in a few cases. 



With oils the use of the Halphen and Bechi tests will be found to be useful a- a 

 means of approximately determining the amounts of adulteration present. If 

 Halphen gives a reaction and Bechi does not, the adulteration with cotton-seed oil 

 is probably less than 20 per cent. 



18. RENARi)'s h TEST FOR PEANUT OIL AS MODIFIED BY TOLMAN. 



Weigh 5 grams of oil into an Erlenmeyer flask, as directed under determination 

 of saponification number. (If this is accurately weighed and a standard solution of 

 alcoholic potash used, the saponification number can be determined on the same sam- 

 ple by titrating the excess of alcoholic potash used in the saponification with half- 

 normal acetic acid.) Saponify with alcoholic potash, naturalize exactly with dilute 

 acetic acid, using phenolphthalein as indicator, and wash into a 500-cc flask con- 

 taining a boiling mixture of 200 cc of water, and 60 cc of a 10 per cent lead acetate 

 solution. Boil for a minute, and then cool the precipitated soap by immersing the 

 flask in water, occasionally giving the flask a whirling motion to cause the soap to 

 stick to the sides of the flask. After the soap has cooled, the water and excess of 

 lead can be poured off, and the soap washed with cold water and with 90 per cent 

 (by volume) alcohol. 1 Now, add 200 cc of ether, cork the flask, and allow to stand 

 for some time until the soap is disintegrated, then heat on the water bath, using a 

 reflux condenser, and boil for about five minutes. In the oils most of the soap will 



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



''Sec appendix, p. 151. 



I Viinnain and Moor, Allen Com. Org. Anal., 3 ed., vol. 2, pt. 1, p. 143. Wesson, Jour. Am. Chern. 

 Soc., 1H95, 17, 724. 



'The addition of ainyl alcohol is not necessary, but the writer finds it very convenient, as it dis- 

 solves the oils or fats and enables one to mix the oil and reagent much hetter. 



Wesson, Jour. Am. Chem. Soc., 1895, 17, 724. A. L. Winton, Conn. Expt. Sta. Kept., 1900. pi. 2 ( 

 P. ll::. 



'Used by th<- writer and found to be nineh more convenient and just as satisfactory as dilute alkali. 

 On, .lour. Am. Chem. Soe., lS'.f>, 17. 721. 



' Kenard, Comp. Kend., ls71, IX. i:',:;o. Benedikt and Lewkovvitseh, ( tils. Fats, and Waxes, p. 8(5. 



i Process u-ed by N. .1. Lane in his modification of Miner's method, .lour. Am. Chem. Soc.. l.x'.i: 1 ,. K, 

 110. 



HUMS No. <;:> 02 3 



