XXVII. METHODS FOR THE DETECTION AND DETERMINATION 

 OF FOOD PRESERVATIVES. PROVISIONAL. 



1. Salicylic Acid. 



A small amount of salicylic acid occurs naturally in many fruits, and not more 

 than 50 grams should be used for its qualitative detection in the examination of 

 foods. A reaction obtained with this amount is due to added salicylic acid. 

 The method described below is intended for the quantitative determination of 

 salicylic acid. If only a qualitative determination be desired, many of the 

 details may be omitted. 



If the material be a solid or semisolid, macerate the sample in a mortar with 

 water made slightly alkaline and strain through a cotton bag or separate by 

 means of a centrifuge. If preferred, macerate from 200 to 300 grams with 

 about 400 cc of water and use aliquots of the filtrate for the determination of 

 preservatives. 



In quantitative work place the macerated mass in a graduated flask, make up 

 to a definite volume with water, and shake from time to time until solution is 

 complete. Then strain as directed above and use an aliquot of the filtrate for 

 extraction. 



Extract in a separatory funnel 100 cc of the sample or of the aqueous solu- 

 tion prepared from the sample as described above with a sufficient amount of 

 sulphuric ether to prevent emulsion after the addition of 2 or 3 cc of dilute 

 (1-3) sulphuric acid. Separate the clear aqueous solution, and if any emulsion 

 is present give the separatory funnel a quick, vigorous shake and allow to settle 

 again. If the emulsion is not broken up in this way, it may be accomplished 



If the nature of the substance Is such that extraction with organic solvents is not 

 practicable, as in the case of the presence of a large amount of fat, the salicylic acid 

 may first be separated by distillation. In such cases acidify the macerated material 

 with phosphoric acid and transfer to a distilling flask with a very short neck and wide 

 mouth. An Erlenmeyer flask with inside diameter of mouth of 1| inches is a good shape. 

 The tube connecting the flask with condenser should be very short, with an inside diame- 

 ter of not less than three-eighths of an inch. 



Conduct steam through a small tube passing through the stopper and dipping deeply 

 into the material in the flask. The distillation of the salicylic acid is facilitated by sub- 

 merging the distillating flask almost to the stopper in an oil bath and distilling with 

 the temperature of the oil at from 120 to 130 C., or by adding about 20 grams of 

 sodium chlorid to the contents of the flask for each 100 cc of the substance, to raise 

 the boiling point. Care must be taken not to let the contents of the flask get too low, 

 as the heat will decompose the organic matter. 



Collect at least 600 cc of the distillate and continue the distillation until the last 

 200 cc gives no color on the addition of a drop of ferric solution. The distilling 

 apparatus should in all cases be tested with known amounts of salicylic acid in order 

 to determine the amount of distillate necessary to carry over a definite weight of 

 salicylic acid. 



It is sometimes practicable to determine the salicylic acid directly In the distillate by 

 the colorimetric method with ferric chlorid given above. If the mineral acid used in 

 the distillation be carried over mechanically, however, the accuracy of the method is 

 greatly impaired. Salicylic acid may be recovered from the distillate after making 

 alkaline and evaporating, if desired, by extraction with ether and estimating colori- 

 metrically as directed above. 



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