164 



A TEXT-BOOK OF BOTANY. 



few exceptions, as Berberine and Sanguinarine, they form mostly 

 colorless crystals. Among the alkaloidal reagents giving charac- 

 teristic precipitates the following may be mentioned. Phospho- 

 molybdic acid ( Sonnenschein's Reagent) gives with nearly all of 

 the alkaloids a yellow, insoluble amorphous precipitate. Potas- 



FIG. 97. Cocaine: A, monoclinic crystals of cocaine; B, orthorhombic crystals of co- 

 caine hydrochloride ; C, monoclinic crystals of cocaine hydrochloride and palladous chloride; 

 D, skeleton aggregates of cocaine hydrochloride and palladous chloride. 



sium mercuric iodide (Mayer's Reagent) precipitates many of 

 the alkaloids in even dilute solutions, the precipitates being usually 

 yellowish-white and more or less flocculent. Wagner's Reagent, 

 or iodine dissolved in a solution of potassium iodide, is another 

 reagent that precipitates nearly all the alkaloids. The precipi- 

 tates are of a reddish or reddish-brown color, and are more 

 readily formed in acidulated solutions. From alcoholic solutions 



