352 



Mr. E. Schunck. 



that the effects observed are due to oxidation. Anyone who has 

 observed the ease and rapidity with which a solution of chlorophyll is 

 bleached on exposure to light and air would be struck with the 

 extraordinary permanence exhibited by phyllocyanin under the 

 same circumstances. A moderately strong solution of phyllocyanin 

 when exposed to sunlight retains its colour for a long time, the last 

 trace disappearing only after many weeks' exposure. 



In order to observe the changes which take place, it is best to 

 take a chloroformic solution of phyllocyanin and expose it to 

 sunlight in a loosely-stoppered bottle, the stopper being occasionally 

 removed, and the contents shaken. The green colour of the solution 

 gradually becomes fainter, the absorption bands of phyllocyanin 

 remaining visible. After some time the colour changes to yellow, but 

 the solution still shows a strong band in the red, corresponding to 

 band I of phyllocyanin. At length this band also disappears, and 

 there is now nothing to be seen but the total obscuration at the 

 blue end of the spectrum, which most yellow solutions show. In 

 one experiment the chloroformic solution was exposed to alternate 

 bright sunlight and diffused daylight from the middle of April to the 

 middle of June, when it was filtered from a flocculent yellow deposit 

 which had formed. A further exposure to the middle of August was 

 required to cause the entire disappearance of the band in the red. 



Several products are formed during this process of insolation. The 

 first consists of a flocculent yellow deposit, which gradually separates 

 from the chloroformic solution. This deposit, after filtering off and 

 washing with chloroform, is found to be easily soluble in alcohol and 

 caustic alkali, but insoluble in boiling water, in which it simply melts ; 

 insoluble also in ether, ligroin, and carbon disulphide. The alcoholic 

 solution is yellow, shows no absorption bands, and leaves, on spon- 

 taneous evaporation, a residue which has a somewhat crystalline 

 appearance, but is found to be amorphous when examined under the 

 microscope. The chloroformic filtrate leaves, on evaporation, a 

 residue, which, on treatment with hot water, dissolves only in part. 

 The part left undissolved by water resembles the product deposited 

 from the chloroformic solution. It melts in boiling water ; it is 

 easily soluble in alcohol, the solution being yellow and leaving, on 

 evaporation, a pale yellow brittle amorphous residue ; it is insoluble in 

 ether and carbon disulphide. The watery filtrate from this second 

 product, after treatment with animal charcoal, which deprives it of 

 most of its colour, leaves, on evaporation over sulphuric acid, a pale 

 yellow transparent gum-like residue, in which nothing crystalline can 

 be detected, and of which the following are the most characteristic 

 reactions : — 



Heated on platinum it is decomposed, giving off acid fumes with 

 an odour like those from heated tartaric acid, leaving much charcoal ; 



