Contributions to the Chemistry of Chlorophyll. 311 



solution gives with acid a greenish-brown precipitate, which is filtered 

 off and dissolved in a little boiling glacial acetic acid. The solution 

 on being left to stand for some days yields a deposit, which is filtered 

 off, washed with a little alcohol, and dried. This product corresponds 

 to the phyllotaonin obtained by the action of alkalis on phyllocyanin, 

 but its properties, though similar, are less characteristic. When dry 

 it appears almost black and amorphous ; under the microscope, how- 

 ever, it is seen to consist in part of prismatic crystals. It is soluble 

 in alcohol, ether, chloroform, and glacial acetic acid, but is insoluble 

 in petroleum ether. The solution in ether has a pink colour, and 

 shows a spectrum consisting of four bands, of which two, viz., one in 

 the red and the other in the green, are very dark. On diluting the 

 solution until only a slight tinge of colour is left, the band. in the 

 green becomes very faint, while that in the red splits up into two 

 nearly equal narrow bands ; the band in the green remains single, 

 however much the solution may be diluted, whereas the analogous 

 derivative of phyllocyanin, after its solution has stood for some time, 

 shows a characteristic double band in this part of the spectrum. 



The description of phylloxanthin just given shows that the pro- 

 perties of the substance closely resemble those of its companion 

 phyllocyanin. Until the composition of the two substances has been 

 ascertained, it is impossible to say in what relation they stand to 

 one another; it is probably a case of isomerism. All attempts to 

 transform phylloxanthin into phyllocyanin, or vice versa, failed. It 

 is certain, however, that the two substances are not formed simul- 

 taneously, unless strong acids, such as hydrochloric, are employed. 

 When, for instance, a little acetic acid is added to an ethereal solu- 

 tion of chlorophyll there is an immediate change of colour in the 

 solution accompanied by the formation of phylloxanthin ; it is only 

 after some time that phyllocj'anin makes its appearance ; at least, such 

 is the conclusion derived from spectroscopic examination of the solu- 

 tion. 



This phenomenon may be explained by supposing that the two 

 substances phyllocyanin and phylloxanthin are formed by the de- 

 composition of two distinct bodies. The researches of Stokes, Sorby, 

 and others have led to the conclusion that ordinary chlorophyll is a 

 mixture of several colouring matters, two of which Mr. Sorby has 

 named " blue chlorophyll " and " yellow chlorophyll " respectively. 

 In a written communication which Sir G. Stokes has kindly addressed 

 to me, he informs me that^he has satisfied himself that by decomposi- 

 tion with acids blue chlorophyll yields phyllocyanin, whereas yellow 

 chlorophyll gives phylloxanthin. This interesting fact affords a 

 striking confirmation of the views held by him regarding the complex 

 nature of chlorophyll. 



The literature of chlorophyll contains descriptions of several sub- 



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