CHROMATOGRAPHY 



149 



larity. A spot of the mixture is placed near the top of a strip of paper. 

 This end is placed in a container of the solvent, with the rest of the paper 

 hanging down over the side. As the solvent moves downward on the sus- 

 pended paper strip, the various pigments are carried along at different 

 rates. This operation is conducted inside a closed container, where the 

 atmosphere is saturated with the solvent vapor. 



Fig. 11-2. Ascending 

 paper chromatography. 

 The mixture of mate- 

 rials was placed along 

 the line (M) and the 

 paper was dried. It was 

 then placed in the test 

 tube, and the solvent 

 ascended by capillary 

 action, having reached 

 point S at the present 

 time. Components 1, 2, 

 3, and 4 have been car- 

 ried upward at different 

 rates. 



'Paper 

 strip 



M 



Solvent 



(4) Solvent is placed in the bottom of a round glass dish. A cone of 

 filter paper is prepared and placed point-up in the center of the dish so 

 that the point of the cone stands just higher than the edge of the dish. 

 Now a disk of filter paper slightly larger than the diameter of the dish 



