6 BULLETIN 448, U. S. DEPARTMENT OF AGRICULTURE. 
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 under the heading 
Separation and Purification of Coloring Substances, page 8. 
Dissolved coloring matters are generally separated from fats and 
oils by saponif}ang the fat or oil with alcoholic potash and extract- 
ing the coloring matter from the soap with gasoline or ether. 1 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. 2 Some dyes, as Anilm Yellow, may 
be extracted from oils conveniently with 90 per cent alcohol. 3 The 
method of Cornelison 4 (extracting the coloring matter with glacial 
acetic acid or with the same solvent containing a little added hydro- 
chloric acid or water) will serve for the extraction of almost all the 
common oil-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 
little gasoline. 
The writer prefers the following procedure, which, though some- 
what inconvenient, is quite generally applicable. 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-boiling 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 liquid with from 50 to 100 cc of ether. The ether is 
first washed a few times with caustic alkali 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 
» See Gruenlmt, Chem. Zentr. 69 (1898) II, 943. 
2 See Berry, U. S. Dept. Agr., Bur. Chem. Circ. No. 25; Doolittle, U. S. Dept. Agr., Bur. Cheni. Bui. 
No. 65, p. 152. 
3 For the extraction and identification of Auramin (No. 425) when present in oils, see Frehse, Ann. fals 
3 (1910), 293. 
* J. Am. Chem. Soc. 30 (1908), 1478. 
