FLAVORING EXTRACTS. 159 



extract. The resins are soluble in 50 per cent alcohol, so that in high-grade 

 extracts, in which sufficient alcohol is used, all of the resins are kept in solu- 

 tion. In cheap extracts, in which as little as 20 per cet of alcohol by volume 

 is sometimes employed, an alkali usually potassium bicarbonate is added to 

 aid in dissolving the resins, gums, etc., and to prevent turbidity. This treatment 

 deepens the color very much. 



(b) DETECTION. 



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

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

 original volume with hot water. If alkali has not been used in the manufacture 

 of the extract, the resins will appear as a flocculent red to brown residue. 

 Acidify with acetic acid to free the resins from the 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 resins in a few cubic centimeters 

 of dilute caustic potash. The resin is dissolved, giving a deep red solution; 

 acidify, and 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 lead subacetate. 

 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 is almost colorless. 



Test another portion of the filtrate from the resin for tannin with a solution 

 of gelatin. Tannin is present in varying but small quantities. It should not be 

 present in great excess. 



10. Detection and Determination of Methyl Alcohol. 

 Proceed as directed under " XV. Distilled Liquors," on page 99, section 12. 



11. Test for Coloring Matter (Caramel). 



(a) PRELIMINARY TEST. 



If on shaking the bottle of vanilla the bubbles formed are of a bright caramel 

 )lor and they keep this color until the very last are gone, it indicates presence 

 caramel. This difference is readily shown by comparison with known pure 

 samples. 



(b) LEAD ACETATE TEST. 



The coloring matter present in vanilla or tonka extracts is almost completely 

 removed when the dealcoholized extract is treated with a few cubic centimeters 

 of basic lead acetate solution. When caramel is present, the filtrate and precipi- 

 tate, if any, have the characteristic red-brown color of caramel. 



LEMON EXTRACT. 

 1. Specific Gravity. 

 Determine as directed under " XIII. Wine," on page 83. 



