CH. Il] CHLOROPHYLL. 51 



colour. The solution which has been exposed to sunlight 

 rapidly becomes brown or yellowish brown, while C 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 1 . 

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



as to remove the air, cork it 2 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 HC1 or HNO 3 to the alcoholic 

 extract and note the appearance of a brownish tint ; with 

 excess of acid a muddy blue or green is produced owing 

 to the precipitation of phyllocyanin and phylloxanthin 3 . 



(59) Action of copper salts. 



By the addition of a little 10% CuS0 4 solution 4 a 

 copper compound is produced, which has the general 

 appearance of chlorophyll, but differs notably in not being 



1 N. J. C. Muller, PringsJieim's Jahrb. vn. p. 205. 



2 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 finished with the test- 

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

 conditions. 



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



4 Or of strong solution of copper acetate and strong HC1. 



42 



