34 BULLETIN 448, U. S. DEPAKTMEXT OE AGEICULTURE. 



have been removed. The precipitate may then be dissolved in hydro- 

 chloric acid of 10 or 15 per cent strength. After whirling again in 

 the centrifuge to separate the lead chlorid thrown out of the solu- 

 tion , the clear red liquid is shaken out once or twice with amyl 

 alcohol to remove various extractives soluble in this substance. It 

 may then be boiled for a short tune, by which means the glucosid 

 is hydrolyzed, the derived coloring matter, or anthocyanidin, being 

 produced. This may now be extracted and obtained in fairly pure 

 solution by shaking out with amyl alcohol. The anthocyanidins, 

 according to Willstaetter/ are oxonium bases, containing also acidic 

 phenolic groups. They are not very readily soluble in amyl alcohol 

 though relatively more so than in aqueous liquids. 



The coloring principles of saffron and of Persian berries also consist 

 chiefly of glucosids, though the lead salts of these are relatively more 

 soluble. These glucosids also are readily hydrolyzed by boiling with 

 acid, but the change in case of saffron is attended with destruction of 

 much coloring matter, at least when the hydrolysis is carried out in 

 the ordinary manner, with free access of air. Berberine is said to be 

 the only common natural basic coloring matter and it is seldom, if 

 ever, found in food products. 



By extraction from neutral solutions with ether, the leaf pigments 

 (identical or similar colors are also found in egg yolk,^ fats and oils,^ 

 carrots, and tomatoes *) are taken up. They are reinoved from this 

 solvent by washing with dilute alkali. 



Coloring matters of alkanet, annatto, turmeric, and of the red dye- 

 woods (sandalwood, camwood, and barwood) a,re very readily and com- 

 pletely extracted by ether from slightly acid solutions. The flavone 

 coloring matters of fustic, of Persian berries (after hydrolysis), and 

 of quercitron, also the coloring matter of brazilwood and the green 

 derivatives formed from chlorophyll by alkali treatment, are taken up 

 in very large proportion by ether from slightly acid solutions. 



The coloring matters of logwood, of archil, of saffron, and of cochi- 

 neal are extracted in relatively small amount by ether from slightly 

 acid solutions, but are largely taken up by amyl alcohol. 



Caramel and the anthocyans constituting the red coloring matters 

 of most common fruits are extracted in relatively small proportion 

 by amyl alcohol from acid solutions. Ammoniacal cochineal (car- 

 mine) is similar, but the ordinary coloring matter is readily re-formed 

 by standing with hydrochloric acid. 



iSitzb. kgl. Preuss. Acad. 12 (1914), 402-411. For further papers by Willstaetter and coworkers see 

 Llebig's Ann. 408 (1915), 1-158. 



2 Willstaetter and Eschar, Zeit. Physiol. Chem. 76, (1912), 214. 



3 See Palmer and Eekles, Mo. Sta. Research Bui., Nos. 9, 10, 11, 12. 



* Willstaetter and StoU, Untersuchmigen ueber Chlorophyll, Berlin (1913). 



