70 PROVISIONAL METHODS FOR ANALYSIS OF FOODS. 



Slightly acidulate the ammoniacal solution reserved for vanillin with 10 per cent 

 hydrochloric acid. Cool and shake out in a separatory funnel with 10 cc of chloro- 

 form, repeating the process as described for ether extraction. Evaporate the 

 chloroform at room temperature and dry over sulphuric acid, or in an air bath at a 

 temperature not exceeding 55. 



Wash the residue with boiling petroleum ether, using 5 to 10 cc at each treatment; 

 'decant the fractions into a dry, weighed evaporating dish. Evaporate the petroleum 

 ether at room temperature and dry as before. Weigh the residue as vanillin. a This 

 should be pure and crystalline and have a melting point of 80 to 81. This, with 

 the characteristic odor and crystalline form, is sufficient for its identification as 

 vanillin. 



5. DISTINCTION OF TRUE EXTRACT OF VANILLA FROM LIQUID PREPARATIONS OF 



VANILLIN. b 



(a) THEORY. 



The leading fragrant principle of the vanilla bean and of true vanilla extract is 

 vanillin, a definite chemical compound hydroxymethoxybenzoic aldehyde. It is 

 not the only fragant or valuable constituent of vanilla bean and true vanilla extracts. 

 The artificial vanillin, made for the market, contains vanillin identical with the 

 vanillin contained in the vanilla bean; but the vanilla bean, as the vanilla extract, 

 contains among its many " extractive matters" which enter into the food and fra- 

 grant value of vanilla, extract, certain resins which can be identified with certainty 

 in analysis by a number of determining reactions. Extract made without true 

 vanilla can be detected by negative results in all these reactions. 



Vanilla beans contain 4 to 11 per cent of this resin. It is of a dark red to brown 

 color and furnishes about one-half the color of the extract of vanilla. This resin is 

 soluble in 50 per cent alcohol, so that in extracts of high grade, where sufficient 

 alcohol is used, all resin is kept in solution. In cheap extracts, where as little as 20 

 per cent of alcohol by volume is sometimes used, an alkali usually potassium bicar- 

 bonate is added to aid in getting resin, gums, etc., in solution, and to prevent sub- 

 sequent turbidity. This treatment deepens the color very materially. 



(b) METHOD OF ANALYSIS. 



Place 50 cc of the extract to be examined in a glass evaporating dish and evaporate 

 the alcohol on the water bath. When alcohol is removed, make up about the 

 original volume w y ith hot water. If alkali has not been used in the manufacture of 

 the extract, the resin will appear as a flocculent red to brown residue. Acidify with 

 acetic acid to free resin from bases, separating the whole of the resin and leaving a 

 partly decolorized, clear supernatant liquid after standing a short time. Collect the 

 resin on a filter, wash with water, and reserve the filtrate for further tests. 



Place a portion of the filter with the attached resin in a few cubic centimeters of 

 dilute caustic potash. The resin is dissolved to a deep red solution. Acidify. The 

 resin is thereby precipitated. 



Dissolve a portion of the resin in alcohol; to one fraction add a few drops of ferric 

 chlorid; no striking coloration is produced. To another portion add hydrochloric 

 acid; again there is little change in color. In alcoholic solution most resins give 

 color reactions with ferric chlorid or hydrochloric acid. 



To a portion of the filtrate obtained above add a few drops of basic lead acetate. 

 The precipitate is so bulky as to almost solidify, due to the excessive amount of 

 organic acids, gums, and other extractive matter. The filtrate from this precipitate 

 i.s nearly, but not quite, colorless. 



'See Appendix, p. 155. * Jour. Am. Chem. Soc., 1899, 21, 719. 



