292 ASSIMILATION, 



coloring-matters of leaves : crystalline substances have been ob- 

 tained, one of which, marked by its blue or bluish-green color, 

 contains about five per cent of nitrogen. 1 



775. Spectrum of chlorophyll. When a ray of white light 

 which has passed through a coloring-matter, for instance, a solu- 

 tion of one of the coal-tar dyes, red wine, or a solution of chlo- 

 rophyll, is examined by means of a spectroscope, certain dark 

 bands, known as the absorption-bands, are observed at definite 

 places in its spectrum. 



776. For convenience in examining the spectra of small 

 amounts of coloring-matters, a direct- vision spectroscope attached 

 to the tube of a microscope is employed, and the coloring-matter 

 in question is placed in a flat-walled bottle or a glass cell on the 

 stage of the microscope. The ray of light which is reflected 

 from the mirror under the stage passes first through the colored 

 matter, next through the objective, and lastly through the prisms 

 which compose the microspectroscopic attachment to the tube. 



777. In order to compare the spectra of different substances; 

 a second prism or set of prisms is often used, by which the spec- 

 trum of a second liquid can be projected by the side of that of 



allowed to stand for five days ; all the chlorophyll pigment is thus removed by 

 the charcoal. Alcohol of 65 per cent strength extracts from the coal a yellow 

 crystallizable substance, while ether or benzine dissolves out matter which, 

 upon evaporation of the solution, yields pure chlorophyll pigment (Comptes 

 Rendus, Ixxxix., 1879, p. 861). By the action of sodium on a benzine solution 

 of the coloring-matter of Primula or of Allium, R. Sachsse has obtained two 

 colored masses. One of these is green, solid at ordinary temperatures, in- 

 soluble in pure water, soluble in a dilute alkali, and also in alcohol and ether; 

 the other, yellow, brittle, crumbling into an orange mass, soluble in the same 

 liquids as the first. Besides these two coloring substances he found also a 

 glucoside (that is, a body which under certain conditions can be split into 

 some one of the sugars and another substance which is capable of further 

 changes). Both of the colored masses can be readily broken up into several 

 different coloring-matters. The matters obtained by this process from the 

 green mass differ from those obtained from the yellow, in containing about 

 three to five per cent of nitrogen, while those from the yellow contain none 

 at all. 



1 The green crystals obtained by the evaporation of a purified solution of 

 chlorophyll in alcohol are called chlorophyllan by Hoppe-Seyler, and chloro- 

 phyll by Gautier. Their analysis reveals the following composition : 

 Hoppe-Seyler. Gautier. 



C 73.345 73.97 



H 9.725 9.80 



9.525 10.33 



N 5.685 4.15 



Ash 1.73 1.75 



