458 



Mr. H. C. Sorby on 



[June 19, 



ing-matters, since it occurs in greater or less quantity in all classes of 

 plants, including fungi. It may be obtained in its most pure state from 

 the orange-coloured antherozoids of Fucus serratus in spring, which exude 

 from the antheridia when the fronds are kept damp. These may be 

 washed off: the fronds into water and separated by filtering, after any coarser 

 particles have subsided. The colouring-matters should then be dissolved 

 out in hot strong alcohol, and the clear solution agitated with bisulphide 

 of carbon. This carries down the orange xanthophyll, which may be 

 somewhat further purified by repeated agitation with fresh alcohol. It 

 may also be obtained from Peltigera canina or from Oscillator 'ice grown in 

 bright light by a similar process ; but in that case, in order to separate 

 the chlorophyll, it is requisite to agitate very many times with fresh 

 spirit and repeated additions of bisulphide of carbon, so as always to 

 leave only a small quantity undissolved. The success of this method 

 depends upon the fact that, unless the relative amount of the orange 

 xanthophyll be too great, the whole is carried down in the bisulphide of 

 carbon, when agitated with spirit of the usual strength. The amount 

 present in the leaves of the higher classes of plants is smaller than in 

 those just named ; but by following the same process a final residue of 

 orange-colour may be obtained, which, however, is seldom free from 

 impurities. When pure and dissolved in bisulphide of carbon, the colour 

 is a slightly pink-orange, and the spectrum shows two obscure absorp- 

 tion-bands in the blue end of the green and green end of the blue. 

 These lie much further from the red end when it is dissolved in absolute 

 alcohol ; and on adding a little hydrochloric acid and turpentine it gra- 

 dually becomes colourless, sometimes turning slightly green ; but this is 

 probably due to the presence of another substance — generally to a trace 

 of yellow xanthophyll. 



Xanthophyll. 



I propose to restrict this name, as applied to an individual substance, 

 to the principal constituent of the mixture which has usually been so 

 called. This generally, if not always, must have been mixed with my 

 yellow xanthophyll and lichnoxanthine. Xanthophyll, as the term is 

 applied by me, may be obtained in the most pure state from Porjphyra 

 vulgaris, by heating in spirit, removing the blue chlorophyll by agitation 

 with bisulphide of carbon, and then adding water to the alcoholic solu- 

 tion, which precipitates the bisulphide along with the xanthophyll. The 

 solution in bisulphide of carbon is of a slightly orange-yellow colour, 

 and gives a spectrum with two absorption-bands between the green and 

 the blue. When dissolved in absolute alcohol they lie at the green end 

 of the blue ; and on addiug a little hydrochloric acid and turpentine the 

 colour gradually disappears, without the production of any new inter- 

 mediate coloured substance, or only such a faint tinge of green as is 

 probably due to impurity. Xanthophyll may also be procured from 

 dark-coloured varieties of Wallflowers (Cheiranthus cheiri), and with more 



