accompanying Chlorophyll, and their Spectroscopic Relations. 179 



" Yellow Chlorophyll," the former being the chief constituent, the 

 latter being present in only a small relative quantity, and each give a 

 series of bands situated throughout the visible portion of the spectrum. 



Hansen's method of isolating the yellow colouring matters is dif- 

 ferent from those of the previous observers. He treats the alcoholic 

 extracts of green leaves with caustic alkali, evaporates the liquor to 

 dryness, and extracts from the residue the yellow colouring matter by 

 means of ether, the study of which lead him to believe that the yellow 

 constituent shows only two bands. 



Schunck obtains from all crude alcoholic chlorophyll extracts minute 

 sparkling red crystals which are deposited on standing, and to which 

 he has not applied a name, but which he considers identical with the 

 erythrophyll of Bougarel and the chrysophyll of Hartsen. On dilution 

 the yellow solutions of these crystals gave two absorption bands in the 

 more refrangible portion of the spectrum, but none in the less re- 

 frangible, and, though not in the same positions as the similar bands 

 (the fifth and sixth) shown by crude chlorophyll solutions, he considers 

 these latter bands not due to chlorophyll but to an accompanying- 

 yellow colouring matter. 



Finally, Tschirch, who used Hansen's method for separating the 

 yellow from the green constituent, describes two yellow colouring 

 matters, to which he gives the names xantho-carotin, showing three 

 bands in the more refrangible part of the spectrum and to which, 

 according to him, the bands in the blue and violet shown by crude 

 chlorophyll solutions are due, and xanthophyll proper, which shows no 

 bands whatever but only a total obscuration in the violet region. 



It will be seen that the results obtained by the various observers do 

 not agree, and a renewed study of the yellow constituent of crude 

 chlorophyll solutions appeared to be desirable. My own results differ in 

 many respects from the hitherto generally accepted ones ; they relate not 

 only to the physical nature of the yellow colouring matters in question, 

 but also enable us to characterise chlorophyll proper in a different 

 manner than was possible before. The preparation of pure chlorophyll 

 seems to baffle all attempts, but so far the physical properties of this 

 substance, the knowledge of which would guide an experimenter in 

 reaching the goal have, as it proves, not been known with sufficient 

 completeness. 



I will now give the results of the experiments I have made, in the 

 endeavour to separate these yellow colouring matters from the accom- 

 panying chlorophyll, dealing more especially with their spectroscopic 

 relations as compared to those of chlorophyll in the violet and ultra- 

 violet region of the spectrum investigated by aid of photography — a 

 means which, with the exception of Tschirch, former observers have 

 not applied — and by which means I have been able to ascertain one or 

 two new facts, and have, I think, been able to clear up the much 



