164 METHODS OF ANALYSIS [Chap. 



SEPARATION OF NATURAL COLORING MATTERS. 



17 Exlraclion with Ether from Neutral Solutions. 



From neutral solutions ether extracts Carotin, Xanthophyll (the pigment found in 

 leaves, fats and oils, egg yolk, carrots, etc.), the coloring matter of tomatoes and 

 paprika and green Chlorophyll. The coloring matter remains in the ether solution 

 on shaking with dilute sodium hydroxid solution or dilute hydrochloric acid, no 

 apparent change taking place although chemically the substances may be altered 

 more or less by this treatment. 



18 Extraction with Ether from Acid Solutions, 



From slightly acid solutions ether extracts very readily and completely the 

 coloring matter of Alkanet, Annatto, Turmeric, and the red dyewoods, Sandalwood, 

 Camwood and Barwood. It extracts in large proportion the flavone coloring matters 

 of Fustic, Persian Berries (after hydrolysis), and Quercitron as well as the coloring 

 matter of Brazilwood and the green derivatives formed from Chlorophyll by alkaline 

 treatment. It extracts in relatively small amount the coloring matters of Logwood, 

 Archil, Saffron and Cochineal. The coloring matters of this group are readily re- 

 moved from ether by shaking with alkaline solutions but in most cases rapidly 

 undergo chemical change. 



19 Extraction with Amijl Alcohol from Acid Solutions. 



From slightly acid solutions amyl alcohol extracts largely the coloring matters of 

 Logwood, Archil, Saffron and Cochineal. [From ammoniacal Cochineal (Carmine) 

 the ordinary coloring matter is readily re-formed upon standing with hydrochloric 

 acid.] Amyl alcohol extracts in relatively small proportions Caramel and the Antho- 

 cyans constituting the red coloring matter of the most common fruits. 



IDENTIFICATION OF NATURAL COLORING MATTERS. 



20 REAGENTS. 



(a) Hydrochloric acid. — Sp. gr. L20. 



(b) 10% sodium or potassium hydroxid solution. 



(C) Sodium hyposulphite solution. — A freshly prepared 5% solution of "Blankite", 

 sodium hyposulphite (Na2S204). 



(d) 0.6% ferric chlorid solution.— Freshly prepared but may be made by diluting a 

 10% stock solution. 



(e) 10%o potassium or ammonium alum, solution. 



(f ) 5% uranium or sodium uranium acetate solution 



(g) Sulphuric acid. — Sp. gr. L84. 



21 PROCEDURE. 



Relatively few good tests are known for the common natural colors. Some of 

 their most useful analytical properties'^ are tabulated in 22. In general these tests 

 should be applied to the somewhat purified solutions of the coloring matter obtained 

 as indicated in 17, 18 or 19. 



Evaporate ether solutions to dryness, warm the residue with a little alcohol and 

 dilute the alcoholic solution with water. Apply the reagents as stated below: 



