Yellow Coloring Matter.—­The simplest experiments show that no analogy exists between the substance which colors flowers yellow and that of which we have already spoken.  The agents which generate so easily with cyanine, the rose-red, violet, or green coloration, cannot in any case impart these colors to the yellow substance obtained from flowers.

By the examination of the various yellow-colored flowers, we have ascertained that they owe their coloration to two substances, which differ from one another in their properties, and appear not to be derived from the same independent principle.  One is completely insoluble in water, which we have termed xanthine, a name which Runge has given to a yellow matter from madder.  As this name has not been accepted in science, we have employed it to denote one of the coloring matters of yellow flowers.  The other substance is very soluble in water, and is by us termed xantheine.

Xanthine, or the Yellow Coloring Matter insoluble in water.—­We have prepared this coloring matter from many yellow flowers, but chiefly from Helianthus annuus.

To obtain it we treat the flowers with boiling absolute alcohol, which dissolves the coloring matter in the heat, and by cooling almost completely allows it again to precipitate.  The yellow deposit which is obtained in this way, is not pure xanthine, as it contains a rather considerable quantity of oil.  To separate this oil we have recourse to a moderate saponification; thus, we heat the yellow precipitate with a small quantity of alkali to saponify the fatty body mixed with the xanthine, which even contains the xanthine dissolved.  As the coloring matter is soluble in the soap solution, we do not treat the mass with water, but decompose it with an acid which isolates the xanthine and the fatty acids resulting from the saponification.  This precipitate we treat with cold alcohol, which leaves behind the fatty acids, and dissolves the xanthine.  This substance is a fine yellow color, insoluble in water, but soluble in alcohol and ether, which are thereby colored golden yellow.  It appears to be uncrystallizable, and possesses the general properties of resins.

Xanthine, in combination with cyanine, modified by the various juices of plants, communicates in variable proportions orange-yellow, scarlet-red, and red colors to flowers.

Xantheine, or the Coloring Matter soluble in water.—­By the preparation of the substance which colors yellow certain dahlias, it is at once perceived that it has no analogy to xanthine.  The latter is as known insoluble in water, while the coloring matter under consideration is readily soluble in water.

To obtain the xanthine we treat the petals of yellow flowering dahlias with alcohol, which quickly dissolves the yellow coloring matter, besides the fat and resin.  The solution is evaporated to dryness, and the residue treated with water, whereby the fat and resin are separated.  The water is again evaporated to dryness, and the residue treated with absolute alcohol.  The resulting solution diluted with water is mixed with neutral acetate of lead, which precipitates the coloring matters.  The lead precipitate is then decomposed with sulphuric acid, upon which the xantheine which remains dissolved in the water is purified by alcohol.