388 



Mr. H. Wager. 



rays of greatest energy and transmits this energy to the molecules of carbon 

 dioxide. 



Again, according to the hypothesis of Usher and Priestley,* the photo-synthesis 

 of carbon dioxide and water is accompanied by the formation of hydrogen 

 peroxide, and it is this latter compound that brings about the bleaching of the 

 chlorophyll. From what we know of photo-chemical activity in other organic 

 compounds, it would, however, not be unlikely that the rays of light absorbed 

 by the chlorophyll may bring about a chemical change in it which is itself 

 sufficient to initiate the series of chemical reactions resulting in the formation 

 of sugar and starch. Thus Hoppe-Seyler,t quoted by Loeb,J " expressed the 

 idea that chlorophyll undergoes first a combination with H 2 C0 3 which, under 

 the influence of light, falls apart in such a way as to yield chlorophyll (or the 

 catalyser contained therein), 2 and a third product, the latter being sugar or 

 a substance from which sugar may be formed." " It is obvious," says Loeb, 

 " that Hoppe-Seyler's idea represents that conception of the action of the 

 catalyser which is more and more supported by the facts." 



Hansen§ suggests that the chlorophyll is capable of forming an unstable 

 compound with carbon dioxide, and that it is then passed on to the plasma 

 of the chlorophyll grain to be converted into carbohydrate. Sir W. N". 

 Hartley,[| in discussing this, says that it is, however, much more probable on 

 chemical grounds that the compound of chlorophyll with carbon dioxide is 

 entirely decomposed, first by the elimination of oxygen, and, secondly, by 

 the elimination of water, so that there are successively formed compounds 

 of chlorophyll (1) with carbon dioxide ; (2) with formic aldehyde ; (3) with 

 glucose ; and, finally, starch, completely formed, is split off the molecule. 



The Bleaching of Chlorophyll in Light. 

 Crude chlorophyll was obtained in the ordinary way by boiling leaves of 

 grass or other plants in water and then extracting with alcohol. Methylated 

 spirit may be used for this purpose, but it is more satisfactory to use 

 absolute alcohol. In order to obtain the chlorophyll in as pure a state as- 

 possible, the strong alcoholic solution was first filtered, then evaporated to 

 dryness, and dissolved in petroleum ether. For many experiments ordinary 

 ether will serve, but for general use petroleum ether is to be preferred. 

 Paper tinged with chlorophyll, either in alcoholic solution or in petroleum 

 ether solution, was used, and also films of chlorophyll made by the evapora- 

 * : Eoy. Soc. Proc.,' vol. 77. 



t ' Physiologische Chemie,' p. 139, Theil I (1877). 

 1 ' Dynamics of Living Matter.' 



§ ' Bied. Centr.,' 1888, see ' Chem. Soc. Journ.,' Abstracts, 1888. 

 || ' Chem. Soc. Journ.,' 1891. 



