1885.] 



The Chemistry of Chlorophyll. 



337 



kind of leaves are taken for extraction, the products are always the 

 same. 



The paper deals only with the properties of phyllocyanin, which are 

 very peculiar. After being purified in the manner described, it is 

 obtained as a dark blue mass resembling indigo, and consisting of 

 microscopic crystals which are generally opaque, but sometimes when 

 very thin are translucent, and then appear olive- coloured. It stands 

 heating to 160° without decomposition, but between that temperature 

 and 180° it is decomposed without previously fusing, leaving a charred 

 mass which on further heating burns away without residue. It contains 

 nitrogen, but is free from sulphur. 



Phyllocyanin is insoluble in water, petroleum ether, and ligroin, 

 but dissolves in alcohol, ether, chloroform, glacial acetic acid, benzol, 

 aniline, and carbon disulphide. The best solvent is chloroform. A 

 minute quantity of the substance imparts an intense colour to any one 

 of these solvents. It is only on diluting largely that the solutions lose 

 their opacity. They then appear of a dull green or olive colour, and 

 show the well-known and often described spectrum of so-called " acid 

 chlorophyll," consisting of five bands, three of which are very dark, 

 one of moderate intensity, and the fifth very faint. 



By oxidising agents, such as nitric or chromic acid, phyllocyanin is 

 easily decomposed, yielding yellow amorphous products, the solutions 

 of which show no absorption bands. It shows a remarkable degree 

 of permanence as compared with chlorophyll, when exposed to the 

 combined action of air and light. A chloroformic solution contained 

 in a loosely stoppered bottle may be exposed for weeks or even months 

 to alternate sunlight and diffused daylight before its peculiar colour 

 and all trace of absorption bands have disappeared. When the 

 process is complete a yellow liquid results, which contains several 

 products, all of them amorphous, one being easily soluble in water and 

 exceedingly bitter to the taste. The decoloration of a chlorophyll solu- 

 tion under the same circumstances would take place in a day or two. 



A small quantity of bromine added to a chloroformic solution of 

 phyllocyanin changes the colour to a bright grass-green, which 

 exactly resembles that of a chlorophyll solution. By a further 

 addition of bromine, the solution loses its green colour and acquires a 

 reddish hue ; it now shows the same spectrum as a phyllocyanin 

 solution ; but the bands are all shifted towards the red end. An 

 excess of bromine produces no further change. On passing chlorine 

 gas through the solution in chloroform, it passes through the same 

 phases of colour, first becoming grass-green, then reddish, but a 

 further change takes place on continuing to pass chlorine through the 

 solution, which now becomes yellow, finally pale yellow, all traces of 

 absorption bands at the same time disappearing. The products both 

 with bromine and chlorine are amorphous. 



