= 12 = 



and aluminum hydroxide carried down the chlorophyll in alcoholic ex= 

 tracts of leaves leaving only the yellow pigments in solutiouo And in 

 1868 Filhol found that animal charcoal or bone black removed the green 

 pigments preferentially from an alcoholic extract of leaves. Addition 

 of charcoal in quantity ins\iff icient to decolorize the extracts yielded 

 a yellow solution containing a mixture of carotenoid pigmentSo 



Separations by Chromatographic Adsorption Analysis 



In 1903 and I906, the Russian botanist Mo Tswett described a 

 particularly selective adsorption procedure that permitted extensive 

 resolution and recovery of the chloroplast pigments o For these sepa- 

 rations, Tswett employed an adsorption column, a glass tube constricted 

 at one end and filled with firmly packed, finely divided, surface-active 

 adsorbents such as powdered inulin, powdered sugar or precipitated chalko 

 VRth the adsorption column attached to a suction flask, a little of a 

 petrolexm ether or carbon disulfide extract of dried leaves was filtered 

 into the coltjmn, wherein the pigments were adsorbed as a narrow band near 

 the top. These adsorbed pigments were then washed with fresh solvent, 

 so that, owing to their selective adsorption, they were carried along 

 at different rates and formed a series of colored zones as indicated in 

 Figure I,l<, The weakly sorbed pigments, principally the carotenes, were 

 washed through the column and collected separately in successive portions 

 of the percolatoo The zones of the more sorbed pigments were removed 

 separately from the column, and the pigments were eluted from the sorbent 

 with alcoholo 



The washing of the narrow zone of adsorbed pigments with fresh 

 solvent was called "die Entwicklung" or development of the chromatogramo 



