1430 FOODS AND FOOD ADULTERANTS. 



0.0025 gram for each 10 cc of 90 per cent alcohol used in the crys- 

 tallization and washing if done at 15; if done at 20, 0.0045 gram for 

 each 10 cc. 



The melting point of arachidic acid obtained in this way is between 

 71 and 72. Twenty times the weight of arachidic acid will give the 

 approximate amount of peanut oil present. 



Another method which gives as satisfactory an approximation of 

 the amount of peanut oil present is to allow the arachidic a acid to 

 crystallize in a 100 cc graduated cylinder and measuring the volume 

 of the precipitate. This volume will have to be determined for the 

 working temperature and the length of time by use of known mix- 

 tures of peanut oil. Cotton-seed and lard oil give slight precipitates 

 when treated by this method. 



Arachidic acid has a characteristic structure and can be detected by 

 the microscope. 



No examination of olive oil is complete without making the test for 

 peanut oil, which probably is the most common adulterant, especially 

 in French and Italian oils. 



BAUDOUIN TEST FOR SESAME OIL. 



Dissolve 0.1 gram of finely powdered sugar in 10 cc hydrochloric 

 acid of sp. gr. 1.20, and add 20 cc of the oil to be tested, shake thor- 

 oughly for aminute, and allow to stand. 



The aqueous solution separates almost at once. In the presence of 

 a very small admixture of sesame oil this is colored crimson. Some 

 olive oils give a pink coloration with this reagent, but they are not 

 hard to distinguish if comparative tests with sesame oil are made. 



Mix 2 grams of furfural with 100 cc 95 per cent alcohol; add 0.1 cc 

 of this solution and 10 cc hydrochloric acid, sp. gr. 1.20, to 10 cc of oil 

 and mix thoroughly by shaking in a test tube; the same color is devel- 

 oped as when the sugar is used. 



The author of this method attributed the Baudouin test to the for- 

 mation of furfural from the action of levulose and hydrochloric acid 

 and so substituted the furfural for the sucrose. 



As furfural gives a violet tint with hydrochloric acid it is necessary 

 to use the very dilute solution given in the method. 



a As the solubility of arachidic acid in 90 percent alcohol increases very rapidly 

 with the temperature, care must be taken to keep the temperature of crystallization 

 down to between 15 and 20, and to obtain satisfactory results the temperature 

 must be same as used in the standards. 



b Villivecchia and Fabris, Journ. Soc. Chem. Ind., 1893, 12, 97 and 1894, 13, 69; 

 Benedikt and Lewkowitsch, Oils, Fats, and Waxes, p. 318, 



