THE CHLOROPHYLL PIGMENT. 291 



cyanin). If considerable alcohol is now added, and the mixture 

 shaken, the liquid again becomes thoroughly mixed and of a 

 clear green color. Fremv's later researches have led him to re- 



c5 / 



gard the so-called plvyllocyanin as really an acid (phyllocyanic), 

 which is probably combined with potassium, and the salt thus 

 formed mixed with phylloxanthin to form the green coloring- 

 matter of chlorophyll. 



(2) IZraus's process. This method of separating the two 

 coloring-matters is based on the action of benzol. The alcoholic 

 solution prepared as directed on page 290, or, much better, with 

 alcohol of 65 %, is shaken with about twice its volume of benzol, 

 or, according to R. Sachsse, with benzin (sp. gr. .714). After 

 a while the turbid liquid separates into a benzol layer above, 

 having a bluish-green color, and an alcohol Ia3~er below, tinged 

 yellow. The yellowish pigment is called by Kraus, xanthophyll, 

 the bluish-green, kyanophyll. According to Wiesner, kyanoplryll 

 is nearly pure chlorophyll freed from its associated 3'ellow pig- 

 ment xanthophyll. It is believed by many that the yellow pig- 

 ment separated by this process is identical with that found in 

 plants blanched (etiolated) in darkness, and which has been 

 called etiolin. 



Different methods (some of which are noticed briefly in the 

 foot-notes l ) have been employed for the isolation of the pure 



1 (1 ) Berzelius evaporates the alcoholic extract to dryness, and after treatment 

 with hydrochloric acid (sp. gr. 1.14), again dissolves it in alcohol. He then 

 precipitates with water, redissolves the precipitate after filtration, and lastly, 

 by acetic acid, precipitates the nearly pure pigment (Aunalen der Chernie und 

 Pharmacie, xxi., 1837, p. 257 ; xxvii., 1838, p. 296.) (2) Fremy throws down 

 from its alcoholic solution, by use of either alumnae or magnesia hydrate, all 

 coloring-matter ; and after thoroughly washing the precipitate dissolves it in 

 alcohol (Comptes Kendus, 1., 1860, p. 405 ; Ixi., 1865, p. 188). (3) Hoppe-Seyler 

 first extracts all waxy matters from green leaves by repeatedly washing them 

 with cold ether, and then treats the leaves with boiling absolute alcohol. After 

 the alcoholic solution has been cooled, again heated, and allowed to stand, red- 

 dish crystals (erythrophyll) separate from it. These are red in transmitted, but 

 green or whitish in reflected light. After their separation the residue of the 

 solution is evaporated to dry ness and again dissolved in ether; from the ether 

 solution, upon slow evaporation, granules are thrown down, which are brown 

 in transmitted and green in reflected light. These granules may be obtained, 

 by repeated solution and by spontaneous evaporation of the solution, in the 

 form of crystals of a high degree of purity, which are called by Hoppe-Seyler 

 chlorophyllan (Zeitschr. phys. Chem., iii. 1879, p. 339). (4) In Gautier's pro- 

 cess, bruised leaves are mixed with sodic hydrate and pressed. After this the 

 residue of the leaves is treated with alcohol at 55 C. , again pressed, and then 

 treated with cold 83 per cent alcohol, all waxy matters being left by the pro- 

 cess undissolved. The alcoholic solution is mixed with animal charcoal and 



