44 FOOD ADULTERATION AND METHODS FOR DETECTION. 



amount of water and a small fragment a little larger than a pinhead 

 of iron alum. The mixture is thoroughly shaken and allowed to stand 

 till the chloroform again settles to the bottom. The presence of 

 salicylic acid is then indicated by the purple color of the upper layer 

 of liquid. 



DETECTION OF BENZOIC ACID. 



Benzoic acid also is used for preserving fruit products. Extract 

 the sample with chloroform as in the case of salicylic acid; remove the 

 chloroform layer and place it in a white saucer, or, better, in a plain 

 glass sauce dish. Set a basin of water as warm as the hand can 

 bear on the outside window ledge and place the dish containing the 

 chloroform extract in it, closing the window until the chloroform has 

 completely evaporated. In this manner the operation may be con- 

 ducted with safety even by one who is not accustomed to handling 

 chloroform. In warm weather the vessel of warm water may, of 

 course, be omitted. Benzoic acid, if present in considerable amount, 

 will now appear in the dish in characteristic flat crystals. On warm- 

 ing the dish the unmistakable irritating odor of benzoic acid may be 

 obtained. This method will detect benzoic acid in tomato catsup or 

 other articles in which it is used in large quantities. It is not suffi- 

 ciently delicate, however, for the smaller amount used with some 

 articles, such as wine. It is often convenient to extract a larger 

 quantity of the sample and divide the chloroform layer into two 

 portions, testing one for salicylic acid and the other for benzoic acid. 



DKTKCTION OF BORIC ACID AND BORAX. 



Boric acid (also called boracic acid) and its compound with sodium 

 (borax) are often used to preserve animal products, such as sausage, 

 butter, and sometimes milk. For the detection of boric acid and 

 borax, solids should be macerated with a small amount of water and 

 strained through a white cotton cloth. The liquid obtained by treat- 

 ing solids in this manner is clarified somewhat by thoroughly chilling 

 and filtering through filter paper. 



In testing butter place a heaping teaspoonful of the sample in a tea- 

 cup. a<l<l a couple of teaspoonfuls of hot water, and stand the cup in a 

 vessel containing a little hot water until the butter is thoroughly, 

 melted. Mix the contents of the cup well by stirring with a teaspoon 

 and set. the cup with the spoon in it in a cold place until the butter is 

 solid. The spoon with the butter (which adheres to it) is now removed 

 from the cup and the turbid liquid remaining strained through a white 

 cotton cloth, or better, through tiller paper. The liquid will not all 

 pass through the cloth or filter paper, but a sufficient amount for the 

 test may be secured readily. 



In testing milk for boric acid '2 or :> tablespoonfuls of milk are 

 placed in a bottle with twice that amount of a solution of a teaspoonful 



