12 BULLETIN 448, U. S. DEPARTMENT OP AGRICULTURE. 



erence. In regard to the presence of alcohol, see page 8. T^Tien large amounts of 

 dissolved foreign material, such as sugar, glycerol, etc., are present, it must be remem- 

 bered that the solubilities of the coloring matters will be somewhat affected. 



Since almost all coloring matters are found accompanied by small amounts of simi- 

 larly colored substances of different solubilities (subsidiary dyes, etc.), it should be 

 made an invariable rule in carrying out the separation, first to follow through, to the 

 point of identification, those coloring matters that seem to be present in largest pro- 

 portion. The course to be pursued in dealing with the smaller fractions will then be 

 more clearly indicated. 



Sec. 1. — The solution containing the coloring matter is treated with enough strong 

 sodium chloiid solution to bring the salt concentration to about 5 or 6 per cent and is 

 then shaken out with 20 cc or more of amyl alcohol . If a considerable amount of color- 

 ing matter is taken up the extraction is repeated once or twice, the different portions 

 of solvent being finally combined. The amyl alcohol, if colored, is washed once or 

 twice with small portions of 5 per cent salt solution, and these washings, if they ap- 

 pear to contain any dye, are added to the original extrac ted solution . Any suspended 

 solid matter that may separate may be considered also to belong to the aqueous solution. ^ 



The amyl alcohol, if colorless or freed from color by the washing, is discarded. 

 Basic dyes and most of the acid colors of low sulphur content are absent. If the amyl 

 alcohol is colored it is treated as directed in section 10. 



Sec. 2. — The extracted salt solution is treated with about one-half its volume of con- 

 centrated hydrochloric acid and is again shaken out with amyl alcohol, exactly as 

 described in section 1. Should coloring matter be extracted, the combined portions 

 of the solvent are washed once with diluted acid (1:2, approximately four-normal), 

 then reserved for treatment as stated under section 6. If the alcohol is colorless, and 

 remains so after treatment with an excess of ammonia solution, it is discarded; and 

 most of the strongly sulphonated azo colors are known to be absent. (^^Tien Naphthol 

 green B is present, compare section 18.) ' 



Sec. 3. — The extracted acid salt solution which may appear nearly colorless is 

 treated with ammonia until slightly alkaline, then made slightly acid with acetic acid. 

 If it is now colorless the absence of the strongly sulphonated triphenylme thane green 

 and blue dyes is shown, and it is discarded. If it is colored, and if the shade indicates 

 the possible presence of green or blue colors, it is shaken out with dichlorhydiin. 

 This solvent is slightly soluble in water, but an amount should be used so that the 

 lower layer after separation will not measure more than 20 cc. If coloring matter of 

 bluish tint has been extracted, the mixture is again shaken out once or twice, and the 

 combined portions of solvent washed with a little salt solution. The dichlorhydrin 

 solution is then examined according to section 5. 



Sec. 4. — The original mixture after the preceding extractions may still contain Acid 

 Magenta, caramel, and many natural colors, especially the glucosids (anthocyans) 

 constituting the common fridt colors. Acid Magenta may be recognized by its reac- 

 tions with nitrous acid, dyeing properties, etc. It may be separated, if desired, by 

 adding hydrochloric acid so that the acidity is above that of a fourth-normal hydro- 

 chloric solution Callowance must be made for the ammonium acetate present) and then 

 shaking out with anilin. The anilin solution is washed with fourth-normal hydro- 

 chloric acid in salt solution of from 5 to 6 per cent strength; and the dye then removed 

 with water, perhaps after addition of some carbon tetrachlorid. Before testing this 

 magenta solution the dissolved anilinmustbecarefully removed, by making alkaline 

 and extracting several times with carbon tetrachlorid, benzene, or other convenient 

 solvent. Commercial Acid Magenta is a somewhat variable mixture of sulphonates 

 and may be expected to yield considerable fractions of lower sulphonated derivatives 

 of greater relative solubility in organic solvents. 



1 The more sy^stematic procedure described in J. Ind. Eng. Chem. 5 (1913), 26, may be iised, if pre- 

 ferred, for this and other similarly described e.x tractions. 



