NON-PROTOPLASMIC CELL CONTENTS 99 
into a yellowish and a greenish portion. ‘The greenish portion 
dissolves in the xylene, which rises, forming the upper stratum, 
while the yellowish portion dissolves in the alcohol and water 
forming the lower stratum. By repeatedly shaking and adding 
alcohol to the greenish fraction it can be entirely separated from 
the yellowish fraction. The isolated greenish portion of alco- 
holic leaf extract has been found to consist of two green pigments 
called chlorophyll a and chlorophyll b. When separated and dis- 
solved in alcohol, chlorophyll a appears blue-green and chlorophyll 
Fic. 55.—Absorption spectrum of five different concentrations of chlorophyll 4. 
The strongest is represented by the lowest spectrum. (From Palladin after 
Willstatter and Stoll.) 
b, yellowish-green in transmitted light. By reflected light, the 
former is blood-red, the latter brownish-red. Chlorophyll a 
constitutes 72 per cent. by weight of the green pigments and has, 
as so far known, the formula of CssH72O;sN4sMg. Chlorophyll 6 
represents the remaining 28 per cent. and has, as far as is known, 
the formula of CssbinOeltaMg— > The isolated yellowish portion 
of the leaf extract consists of two pigments, carotin and xanthophyll. 
Alcoholic solution of chlorophyll, when examined spectro- 
scopically in several concentrations, shows absorption bands in 
the red, orange, yellow and green with a diffuse band in the 
