118 CHLOEOPHTLLINE CHEOMULES. 



a normal green alcoholic solution of chloropliyll, whilst the other sol- 

 vent should be one that will not chemically unite with alcohol, such 

 as benzol, carbon disulphide, or some fatty or ethereal oil. The 

 liquids are intimately mixed by shaking. Mter separation the alcohol 

 of the original solution will no longer appear green, but more or less 

 yellow, whilst the other solvent will show a grass-green or glaucous 

 colour. Those two chromules are looked upon as the pure components 

 of leaf- green. The yellow portion dissolved in the alcohol does not pos- 

 sess the optical marks of chlorophyll, whilst the glaucous component, 

 though supposed to possess the essential characteristics of chlorophyll, 

 is still believed to distinguish itself from the original solution. 



The opinion that chlorophyll is a compound, its colour being due 

 to the two constituent elements, has received important support, and 

 indeed seemed completely confirmed by the yet unrefuted assertion of 

 Kraus, that the absorptions of the two components are combined in the 

 chlorophyll spectrum. Kraus also affirms that the yellow component 

 has absorptions only in the blue, and the green or glaucous compo- 

 nent in both halves of the spectrum, which is undeniable ; yet those 

 in the second half are obviously displaced. He believes that the 

 first four bands in, the chlorophyll spectrum are entirely due to the 

 glaucous component, and that the continuous absorption shown by 

 unseparated chlorophyll is simply a combination of the somewhat 

 differently situated bands of the two components. These assertions, 

 however, require considerable corrections. 



Certain conditions are necessary for the proper observation of these 

 phenomena. The first to be mentioned is that the added solvent must 

 not be perfectly miscible with the alcohol of the chlorophyll solu- 

 tion, which depends on the dilution of the alcohol. Thus, e.g., benzol 

 mixes freely with alcohol of 90 per cent, strength. With weaker alcohol 

 the phenomenon always presents itself, but its distinctness depends on 

 the degree of dilution of the alcohol, on the relative proportions of 

 alcohol and benzol, and also whether more or less benzol is retained 

 in solution by the alcohol. A. certain amount of dilution of the alcohol 

 is an advantage therefore by keeping the alcohol and benzol portions 

 as separate as possible ; too much water, on the other hand, is apt to 

 produce turbidity on the addition of the benzol. 



As to the colours which make their appearance, it is important 

 to remember that benzol, carbon disulphide, various fatty and ethereal 

 oils, certain acids, &c., are able to absorb many times more chlorophyll 

 than even high-percentaged alcohol, and are accordingly tinged much 

 more deeply. 



The disregard of these conditions has given rise to much dispute 

 as to the proper colour of the green component. 



The yellow colour of the alcoholic portion is also influenced, but 

 in a reverse manner, of course. As already remarked the yellow 

 alcoholic portion of chlorophyll is believed to have absorptions only 

 in the second half of the spectrum, but a closer examination reveals 

 also the characteristic chlorophyll bands in the first half. In a few 

 cases Kraus appears to have noticed a trace of the chlorophyll band I., 

 from which he inferred that the chlorophyll had not been completely 

 eliminated from the yellow chromule. Bat we have never succeeded 

 in obtaiuiug a yellow alcoholic portion which had no chlorophyll 



