MICR O CHE MIS TR Y. 



tration, while the solution of carotin in carbon bisulphide, 

 as already stated, is always blood-red. 



The absorption spectrum of carotin shows, according to 

 Immendorff (I, 510), two bands in the blue and absorption 

 of the violet. 



y. Xa n t h i n. 



173' Xanthin occurs in the yellow chromoplasts, always 

 in amorphous form, and especially in small granules (grana) 

 (cf. 357). Its alcoholic solution leaves, on evaporation, 

 according to Courchet (I, 349), a wholly amorphous, resin- 

 like mass. It is insoluble in water, little soluble in ether, 

 chloroform, and benzine, but more so in alcoJiol. With con- 

 centrated stilphuric acid, the isolated pigment, as well as the 

 chromoplast, takes first a greenish, then a blue color ; with 

 iodine, best used in the form of the solution with potassium 

 iodide, it becomes green. 



6\ Coloring Matter of Aloe Flowers. 



174. A coloring matter whose reactions differ essentially 

 from those of xanthin and carotin has been recognized by 

 Courchet (I) in the chromoplasts of the flowers of Aloe~ 

 It is insoluble in ether and chloroform, but readily so in 

 alcohol, with a currant-red color. On dilution its solution 

 becomes rose-red ; benzine takes up but little of it ; and it 

 has not yet been obtained in crystalline form. It becomes 

 yellowish green with sulphuric acid, and about the same with 

 hydrochloric acid ; nitric acid first turns it yellow and then 

 decomposes it. Caustic potash colors the granules of the 

 coloring matter orange and makes them run together ; 

 iodine colors them dirty yellow. 



This substance has not yet been observed in other plants. 



e. Coloring Matters of the Chromatophores of the 

 Flor idea . 



175. In the chromatophores of the Floridea there occur a 

 red pigment soluble in water and a green pigment soluble 

 in alcohol. The latter is almost certainly identical with 



