FOOD-COLORING SUBSTANCES. 55 
Ferric chlorid gives no marked change with annatto, turmeric, 
or saffron, these perhaps, appearing somewhat browner. With the 
flavone colors, colorations varying from dark olive green to black 
are produced. With the redwoods and logwood, very dark shades of 
violet, brown, or black are obtained. Cochineal becomes somewhat 
darker. Caramel is not affected. The solutions must be practically 
neutral. 
By addition of alum solution the yellow color of logwood is changed 
to rose red (rather slowly). The redwoods are affected similarly. 
The pale yellow solutions of the flavones become more strongly 
yellow, that of fustic developing a green fluorescence. Saffron and 
turmeric show little change. 
Uranium acetate in neutral or nearly neutral solutions gives 
orange colorations with the flavones. Turmeric becomes somewhat 
browner; saffron is not affected; cochineal becomes green; alkanet, 
yellowish green to bluish green; logwood, violet, quickly fading. 
The coloration with concentrated sulphuric acid dropped on the 
dry coloring matter is for carotin and xanthophyll, blue, usually 
obtained with difficulty. Annatto and saffron also give blue colors; 
turmeric, a red; the flavone colors, yellow or orange colorations; 
alkanet and archil give violet blue; logwood, red, changing to yellow. 
The "brown phase" reaction 1 may be useful for the characteriza- 
tion of chlorophyll, when this has not been previously treated with 
alkalies. The green ether or petroleum ether solution of the coloring 
matter, when treated with a little methyl alcohol solution of potas- 
sium hydroxid, becomes brown, returning to green in a few moments. 
The characteristic reaction of curcumin (turmeric) with boric 
acid may be conveniently carried out as follows : The aqueous or 
dilute alcoholic solution of the color is treated with hydrochloric acid 
until the shade just begins to appear slightly orange. The mixture 
is then divided into two parts and some boric acid powder or crystals 
added to one part. A marked reddening quickly will be apparent, best 
seen by comparison with the portion to which the boric acid has not 
been added. 2 
i Molisch, Ber. bot. Ges. 14 (1896), 16. Willstaetter and Stoll, Untersuchungen ueber Chlorophyll. 
Berlin, 1913, p. 144. 
2 The properties of pure preparations of the various natural coloring matters, as described by the nu- 
merous investigators who have isolated and studied them, are described for the most part in H. Rupe's 
Chemie der Naturlichen Farbstoffe, Braunschweig, 1900 and 1909. Properties of the chlorophylls and 
cartinoids are given by Willstaetter and Stoll, Untersuchungen ueber Chlorophyll , Berlin, 1913; those of the 
coloring matters of the cornflower, rose, pelargona flower, larkspur, cranberry, whortleberry, and purple 
grape, are described by Willstaetter and coworkers. Sitzb. kgl. Pruess. Akad. 12 (1914), 402, Liebigs 
Ann. d. Chem. 408 (1915) 1. 
