44 CHLOROPHYLL. [CH. H 



(56) Action of light. 



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

 them and place A in sunlight/ B in difSFused 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 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, 5 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 far more 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. 

 If the extract is boiled for too long a period it becomes 

 more concentrated and therefore of a darker tint than the 

 unboiled sample, this may be rectified by dilution with 

 boiled alcohol before exposure to light. 



(58) Action of acid. 



Add a few drops of HCl to the alcoholic extract and 

 note the appearance of a brownish tint (phyllocyanin) ; 

 with excess of acid a muddy blue is produced. 



(59) Action of copper salts. 



By the addition of a little 10 "/o CuSi^ solution a 

 1 Or of strong solution of copper acetate and strong HCl. 



