PROPERTIES AND METHODS OF IDENTIFICATION 229 



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methyl alcohol. They arc readily adsorbed from petroleum ether by 

 C'aCO. and more readily adsorbed from carbon disulfide by CaC0 3 

 than xanthophyll a. The carbon disulfide solutions are yellow to 

 orange. The piuiuents are readily released from adsorption on CaC0 3 

 by benzene and when thus adsorbed in a chromatograrri may be 

 separated from each other by this solvent. The action of concen- 

 trated mineral acids from the alcoholic solution of these xanthophylls 

 is not known, but it may be similar to that on xanthophyll (3. The 

 absorption bands of these xanthophylls is stated by Tswett to be 

 shifted slightly towards the violet from those of xanthophyll a. The 

 measurements of these bands has not been reported. 



Xanthophyll ft. This carotinoid, like the other xanthophylls, is 

 quantitatively extracted from petroleum ether by 80-90 per cent alco- 

 hol. It forms almost undissociable adsorption compounds with CaC0 3 

 when in petroleum ether or carbon disulfide, but can be released from 

 this combination by petroleum ether containing 10 per cent absolute 

 alcohol. Concentrated mineral acids produce a green color, passing 

 to a peacock blue when added to its alcoholic solution. NH 4 OH will 

 restore the yellow color and acid the blue color. The reaction is similar 

 to one shown by fucoxanthin, in which a hydrochloride is formed, and 

 in w r hich the yellow pigment restored by alkali still retains one mole- 

 cule of HC1. The absorption bands of alcoholic solutions of xan- 

 thophyll (3 lie at 475-462|i[.i and 445-43 lp|i, which are seen to be 

 shifted appreciably towards the violet from the bands of crystalline 

 xanthophyll. 



Rhodoxanthin. This red isomer of the xanthophylls is known 

 largely through the properties of its solutions, pure crystals of the 

 pigment not yet having been obtained in sufficient quantity for 

 analysis. This carotinoid forms yellow solutions in petroleum ether, 

 ether and benzene, like other carotinoids, but its alcoholic and acetone 

 solutions are rose colored or pink. It is also dissolved by glacial 

 acetic acid with a red color. The red color in certain solvents serves 

 to distinguish the pigment from other carotinoids, as does also the 

 ruby red or violet red color in carbon disulfide. Formic acid also 

 dissolves the pigment, at first with a pink color which later turns 

 yellow. 



Rhodoxanthin, in common with other carotinoids, is not readily at- 

 tacked by alkali. Its xanthophyll-like character is shown by the fact 

 that 80 per cent alcohol quantitatively extracts the pigment from its 

 solution in petroleum ether. In common with crystalline xanthophyll 



