CH. Il] CHLOROPHYLL. 51 



(56) Action of light \ 



Fill three test-tubes with alcoholic leaf-extract, cork 

 them and place A in sunlight, B in diffused light, G 

 in the dark. After a few hours note the changes in 

 colour. The solution which has been exposed to sunlight 

 rapidly becomes brown or yellowish brown, while G is 

 unchanged and B is intermediate in tint. In the absence 

 of sunlight the effect may be shown by placing A close to 

 the window, B in a dull corner, and G in the dark. 

 Exposure for 24 hours is necessary. Chlorophyll solution 

 may be compared with an alcoholic extract of etiolin, 

 which is almost completely stable in light. 



(57) Aeration in connection with the action of light'^. 

 Boil some of the alcoholic solution in a test-tube, so 



as to remove the air, cork it ^ and allow it to cool. Place 

 it with an unboiled sample in bright diffused light, and 

 note that the absence of oxygen delays the light effect. 



(58) Action of acid. 



Add a few drops of HCl to the alcoholic extract and 

 note the appearance of a brownish tint ; with excess of 

 acid a muddy blue is produced owing to the precipitation 

 of phyllocyanin and phylloxanthin^ 



1 Sachs' Bot. Zeitung, 1864; Physiologie (French Trans.), 1868, p. 13; 

 Wiesner, Sitz. Wien. Akad. voL lxix. 1874. 



- N. J. C. Miiller, Pringsheim^s Jahrb. vii. p. 205. 



3 To cork a full test-tube, the best plan is to include a piece of thin 

 wire between the cork and the glass ; this makes a vent for the escape of 

 the fluid, which closes when the wire is pulled out. To prevent the 

 entrance of air the operation of corking should be jiiiished with the test- 

 tube inverted in a fluid, and the wire should be pulled out under the same 

 conditions. 



^ See Schunck, Annals of Botany, in. p. 88. 



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