ipisl Clarence J. West i57 



substance, the test being a different adsorption spectrum) distin- 

 guishes four xanthophylls, et, a', a", and ^3. He believes the xan- 

 thophyll of Willstätter and Mieg is an isomorphous mixture of two 

 or three xanthophylls, with the a-form predominating. Unfortu- 

 nately the method does not seem to permit of the isolation of the 

 individual pigments in quantity large enough for chemical investi- 

 gation. It is entirely possible that Tswett is right and that there 

 is present in the chloroplast a mixture of very similar isomorphic 

 and isomeric xanthophylls, for the Separation of which we have as 

 yet no preparative method. This is all the more plausible when we 

 consider the slight differences between Carotin and lycopin; and the 

 similarity of xanthophyll and lutein (described below). On the 

 other hand, these Compounds are rather easily oxidized and the 

 slight differences in the absorption spectra may be due to changes in 

 the xanthophyll by oxidation. 



Xanthophyll is found in the alcoholic extract of the leaves. 

 Attempts to obtain it pure, in which the Chlorophyll was isolated 

 as the magnesium-free derivative, pheophytin, by treatment of the 

 extract with oxalic acid, always gave negative results. This is prob- 

 ably because the xanthophyll is changed by the acid into a more 

 easily soluble and non-crystalline substance. Better results were 

 obtained when the mother liquor of potassium chlorophyllin was 

 used. For example, the extract from loo k. of nettle leaves, after 

 removal of the potassium salt by filtration and further precipitation 

 with a large quantity of ether, was washed free from alcohol with 

 water, the deep yellow ether sol. evaporated to about 6 1., washed 

 repeatedly with alcoholic potash sol. and water, dried with sodium 

 Sulfate and mixed with 2 vol. of petroleum ether. The xantho- 

 phyll was purified by extraction with 1200 cc. of boiling acetone, 

 and precipitated with 2 vol. of methyl alcohol. Recrystallized from 

 methyl alcohol, about 12 gm. of xanthophyll were obtained. 



Willstätter and Stoll have also described methods for the prepa- 

 ration of xanthophyll from the mother liquors of Chlorophyll and 

 of crystalline Chlorophyll. These depend upon the removal of 

 xanthophyll, from the petroleum ether sol., with dilute methyl alco- 

 hol (80-90 percent), the Carotin and Chlorophyll remaining in the 

 petroleum ether. This is also the basis of the quantitative estima- 

 tion of the various plant pigments. The two yellow pigments make 

 up from o.i to 0.2 percent of the dry weight of the leaf, of which 



