X] FOOD PRESERVATIVES 145 



each time. The chloroform layer usually separates readily after standing a few 

 minutes. If an emulsion forms, break it: (1) by stirring the chloroform layer with 

 a glass rod; (2) by drawing it off into a second fimnel and giving 1 or 2 sharp shakes 

 from one end of the funnel to the other; or (3) by centrifugalizing for a few moments. 

 As this is a progressive extraction, draw off carefully as much of the clear chloro- 

 form solution as possible after each extraction, but do not draw off any of the emul- 

 sion with the chloroform layer. If this precaution is taken, the chloroform extract 

 need not be washed. 



Transfer the combined chloroform extracts to a porcelain evaporating dish, 

 rinse the container several times with a few cc. of chloroform, and evaporate to 

 dryness at room temperature in a current of air dried over calcium chlorid. 



The extract may also be transferred from the separator^ funnel to a 300 cc. Erlen- 

 meyer flask, rinsing the separatory funnel 3 times with 5-10 cc. of chloroform. Dis- 

 til very carefully to about one fourth the original volume, keeping the temperature 

 down so that the chloroform comes over in drops, not in a steady stream. Then 

 transfer the residue to a porcelain evaporating dish, rinsing the flask 3 times with 

 5-10 cc. portions of chloroform, and allow to evaporate to dryness spontaneously. 



Dry the residue overnight (or until no odor of acetic acid can be detected if the 

 product is a ketchup) in a desiccator containing sulphuric acid. Dissolve the resi- 

 due of benzoic acid in 30-50 cc. of neutral alcohol, add about one fourth this volume 

 of water, 1 or 2 drops of phenolphthalein, and titrate with N/20 sodium hydroxid 

 (1 cc. is equivalent to 0.0072 gram of anhydrous sodium benzoate). 



SACCHARIN. 



12 Qualilative Test. 



Extract with ether (after maceration and exhaustion with water, if necessary), 

 as directed in 1 and 4. Allow the ether extract to evaporate spontaneously and 

 note the taste of the residue. The presence of saccharin, to the extent of 20 mg. 

 per liter, is indicated by a sweet taste. Confirm by heating with sodium hydroxid, 

 as described below, and detecting the salicylic acid formed thereby. A sweet taste, 

 suggesting the presence of a trare of saccharin, has been obtained frequently in 

 saccharin-free wines, due to the so-called "false saccharin". 



Acidify 50 cc. of a liquid food or the aqueous extract of 50 grams of a solid or semi- 

 solid, prepared as directed in 1 (C), and extract with ether as directed in 13. Dis- 

 solve the residue, remaining after evaporation of the ether, in a little hot water 

 and test a small portion of this solution for salicylic acid as directed under 2 or 3. 

 Dilute the remainder of the solution to about 10 cc, and add 2 cc. of sulphuric 

 acid (1 to 3). Heat to boiling and add a slight excess of 5% potassium perman- 

 ganate solution, drop by drop; partly cool the solution, dissolve a piece of sodium 

 hydroxid in it, and filter the mixture into a silver dish (silver crucible lids are well 

 adapted to the purpose); evaporate to dryness and heat for 20 minutes at 210"- 

 215°C. Dissolve the residue in water, acidify with hydrochloric acid and test the 

 ether extract for salicylic acid as directed under 2 or 3. By this method all the 

 so-called "false saccharin" and the salicylic acid naturally present (also added 

 salicylic acid when not present in too large an amount) are destroyed, while 5 mg. 

 of saccharin per liter are detected with certainty. 



13 Quantilalive Method. 



Pipette 100 cc. of the sample, or a convenient portion of a solution, prepared 

 as directed under 1 , representing not less than 20 grams of the sample, into a sepa- 



