COLORING MATTER. 199 



7. Determination of Vegetable Colors. 



A great many tests for vegetable colors are given, depending largely on color 

 reactions with different reagents, but these must be used with very great dis- 

 crimination, as they depend very largely on a fine judgment of shades of colors 

 which many eyes are not able to distinguish. 



A great deal of work has been done on detection of vegetable colors,** but in 

 only a very few cases are the reactions specific enough to be decisive. 



8. Detection of Turmeric. & 



Extract the color with alcohol. Dip a piece of filter paper" into this tincture 

 and dry at 100 C. 



Then moisten in a weak solution of boric acid to which a few drops of hydro- 

 chloric acid have been added. On drying this a cherry-red color will be 

 developed in the presence of turmeric, which is characteristic. 



9. Detection of Caramel, 

 (a) AMTHOB TEST.C 



Place 10 cc of the solution to be tested in a high narrow glass with per- 

 pendicular sides, as, for example, a small bottle; add from 30 to 50 cc of 

 paraldehyde, depending on the intensity of the coloring, and enough absolute 

 alcohol to make the solutions mix. In the presence of caramel a brownish- 

 yellow to dark-brown precipitate will collect in the bottom of the glass. Decant 

 the liquor, wash once with absolute alcohol, dissolve in a small amount of hot 

 water, and filter. The color of this solution will give some idea of the amount 

 of caramel present 



It is not allowable to concentrate the solution by evaporation on a steam 

 bath, as caramel may be formed ; if it is necessary to concentrate, it must be 

 done over sulphuric acid or at diminished pressure. 



In order to identify the color, pour the solution into a freshly prepared solu- 

 tion of phenylhydrazin (2 parts phenylhydrazin-hydrochloric, 3 parts sodium 

 acetate, and 20 parts of water). The presence of a considerable quantity of 

 caramel gives a dark-brown precipitate in the cold, which is hastened by heat- 

 ing a little. In the case of a very small amount it takes some hours for it to 

 collect. 



(b) CRAMPTON AND SIMONS' FULLER'S EARTH METHOD.** 



Add 25 grams of fuller's earth to 50 cc of the sample under examination, 

 beat the mixture in a beaker, and let it stand covered half an hour at room 

 temperature, then filter. The determination of the figure representing the color 

 is made with the tintometer upon the liquid before and after treatment and 

 the difference between the two results gives the percentage of color absorbed. 



a Girard and Dupre", Analyse des matieres alimentaires, etc., 580-581, also 169 ; A. W. 

 ttlythe, Foods, their Composition and Analysis, p. 91-109 ; Allen, Commercial Organic 

 Analysis, 3 (1) : p. 376. Burcker, Traite des falsifications et alterations des substances 

 alimentaires, et des boissons, p. 160; W. Lenz, Zts. anal. Chem., 1885, 24: 285. 



"Allen, Commercial Organic Analysis, 3 (1) : p. 359; U. S. Dept Agr., Division of 

 Chemistry, Bui. 51, p. 131. 



r Zts. anal. Chem., 1885, 24: 30; Borgmann, Analyse des Welnes, p. 98. 



* J. Amer. Chem. Soc., 1899, 21 : 355. 



