21 



solvent, evaporate to dryness, and examine the color residue by the schemes given 

 in the following references, consulting the tables of Schultz and Julius. 



Witt, Analyst, 11, 111. 



Allen, Com. Org. Anal., 3, (1), 399-420. 



VVeingartner, J. Soc. Dyers, 3, 67. 



Dommergue, Zts. anal. Chem., 1887, 26, 100; J. Soc. Chem. Ind., 8, 216. 



Girard, Zts. anal. Chem., 1888, 87, 232. 



Dupre, Zts. anal. Chem., 1890, 29, 369. 



Girard and Pabst, Compt. rend., 101, 156. 



Sorby, Proc. Royal Soc. No. 92, 1867. 



Schoop, J. Soc. Dyers, 2, 7. 



Stein, Dingl. Polyt. J., 210, 245. 



Goppelsroeder, J. Soc. Dyers, 4, 5. 



Fol, J. Chem. Soc., 28, 193. 



Hummel and Lepetit, J. Soc. Dyers, 4, 133. 



Leach, Food Inspection and Analysis, New York, 1904. A table including about 50 

 selected coloring matters which are adapted for and have been found in foods by 

 various analysts, as listed in State and Government reports, as well as in laws of 

 various countries dealing with food colors. 



Most colors may be conveniently narrowed down to groups and classes by the 

 scheme devised bv Rota, given in Provisional Methods of Food Analysis. & 



e. SPECIAL TESTS FOR COAL-TAR COLORS. 

 1. Determination of add magenta Girard's method. 



Girard and Dupre, Analyse des matieres alimentaires, etc., p. 169; Winton, Conn. 

 Agr. Expt. Sta. Rept., 1899 (2), 132; Tolman, U. S. Dept. Agr., Div. of Chem., Bui. 

 65, p. 114. 



2. Test for Martins yellow or naphthalene yellow. 

 Tolman, loco cit. 



3. Test for naphthol colors, c 



Fifty cc of wine are acidified with a few drops of hydrochloric acid and wool yarn 

 placed in the liquid. Boil one-fourth hour. Wash the wool with water and then 

 boil in fresh water with a few drops of hydrochloric acid for another one-fourth 

 hour. Wash the wool thoroughly with water and warm with fresh water containing 

 a few drops of ammonia to dissolve the dye. The solution becomes red. Acidify 

 the ammoniacal solution with hydrochloric acid and dye another piece of wool. 

 Examine the dyed wool for identity of dye. 



4. Test for Bordeaux red.d 



Casali found that the artificial coloring of Italian wines was a very general' prac- 

 tice, those from the central provinces being chiefly colored with a " Vinoline" red 

 and those from the south with Bordeaux red (azo-naphthyl-naphthol sulphonic acid). 

 Treat 50-100 cc of wine with 10-20 per cent of a 10 per cent solution of barium chlorid 

 and sufficient potassium bisulphate solution to precipitate the barium introduced. 

 When the precipitate has subsided, decant the supernatant liquid, add 3-6 cc of 

 hydrochloric acid and sufficient water to restore to its original volume, and boil for 

 five to ten minutes with a little fat-free wool. In the presence of Bordeaux red the 

 wool is dyed a bright red color, which does not change on adding ammonia. 



Tabellarische Ubersicht der kunstlichen organischen Farbstoffe, 4th ed., Berlin, 

 1902; revised 2d ed. in English, by A. G. Green. 



&U. S. Dept. Agr., Bureau of Chemistry, Bui.. 65, p. 115. 

 c Fresenius, Anleitung zur chem. Analyse des Weines, p. 92. 

 <*Staz. Speriment. Agrar. ItaL, 1900, 33, (2), 183-189. 



