6 BULLETIN 448, U. S. DEPARTMEN'T OF AGEICULTUEE. 



The amyl alcohol containing the color is washed a few times with a 

 salt solution containing hydrocholoric acid to remove the protein; one 

 separation with the centrifuge usually being desirable to free the 

 solvent from the coagulum. The further treatment of the amyl 

 alcohol solution is the same as that described mider the heading 

 Separation and Purification of Colormg Substances, page 8. 



Dissolved coloring matters are generally separated from fats and 

 oils by saponifying the fat or oil with alcoholic potash and extract- 

 ing the coloring matter from the soap with gasohne or ether.^ The 

 manipulation of this process is not very convenient and, of course, 

 all unsaponifiable matter remains with the color. It may be com- 

 bined with advantage in many cases with one of the extraction 

 methods with an immiscible solvent described below. A number 

 of extraction methods are in use and probably each possesses 

 advantages for certain colors.^ Some dyes, as Andin Yellow, may 

 be extracted from oils conveniently with 90 per cent alcohol.^ The 

 method of Cornehson * (extracting the coloring matter with glacial 

 acetic acid or with the same solvent containing a Httle added hydro- 

 chloric acid or water) will serve for the extraction of almost all the 

 common od-soluble dyes. Much oil dissolves in the acetic acid and 

 a systematic fractionation is necessary; the different portions of 

 extract being washed successively in several funnels containing a 

 httle gasohne. 



The writer prefers the following procedure, which, though some- 

 what inconvenient, is quite generally apphcable. It does not give a 

 color entirely free from cholesterol and similar compounds. About 

 30 cc of the oil are diluted with about 120 cc of low-boihng gasoline, 

 and this mixture is shaken out with several portions of a mixture of 

 90 parts of phenol with 10 of water. The volume of the first portion 

 of solvent may be about 45 cc, the others 30 cc each. The phenol 

 extract is washed in a separatory funnel with 2 or 3 portions of gaso- 

 line, then treated with sufficient cool, strong potassium or sodium 

 hydroxid solution to dissolve the phenol. The dye is removed by 

 shaking out the hquid with from 50 to 100 cc of ether. The ether is 

 first washed a few times with caustic alkafi solution to remove all 

 phenol and finally with water. It may then be evaporated or treated 

 further as indicated on pages 7 and 32-33. 



The Sudan dyes are readily extracted by a mixture of 80 parts 

 phosphoric acid (85 per cent, density about 1.70) and 20 parts con- 

 centrated sulphuric acid. The oil containing the dyes should be 



1 See Gruenhut, Chem. Zentr. 69 (1898) II, 943. 



2 See Berry, U. S. Dept. Agr., Bur. Chem. Circ. No. 25; Doolittle, U. S. Dept. Agr., Biir. Cheni. Bui. 

 No. 6.5, p. 152. 



5 For the extraction and identification of Auramin (No. 425) when present in oils, see Frehse, Ann. fals 

 3 (1910), 293. 



* J. Am. Chem. See. 30 (1908), 1478. 



