46 THE SYNTHESIS OF CARBOHYDRATES 



films of chlorophyll exposed to an atmosphere of carbon dioxide 

 in sunlight, was shown by Wager* and Warner f to be faulty, 

 inasmuch, as Wager showed, that no formaldehyde was pro- 

 duced if oxygen was excluded, whilst Warner showed that 

 carbon dioxide was unnecessary and took no part in the pro- 

 duction of the formaldehyde. Warner concluded that the 

 formaldehyde was in fact an oxidation product of the chlorophyll 

 since oxygen was actually absorbed in the process. This view 

 has, however, since been superseded by the experiments of Will- 

 statter and Stoll who showed that no formaldehyde at all was 

 formed if pure chlorophyll in colloidal solution was employed, 

 the colloidal solution being considered to approximate most 

 closely to the condition of the chlorophyll in the chloroplast. 

 The formaldehyde described by the earlier workers is attri- 

 buted to the oxidation of impurities accompanying the samples 

 of chlorophyll used by them. 



The failure to obtain any trace of formaldehyde from pure 

 chlorophyll in vitro is attributed by Willstatter and Stoll to 

 the absence of the essential enzyme which these authors postu- 

 late in the green leaf, and this brings us to the consideration 

 of the mechanism of the action of chlorophyll upon carbon 

 dioxide as visualized by these authors. 



Experiments in vitro have shown that carbon dioxide can 

 form with chlorophyll (I.) in colloidal solution an additive 

 compound of the type of a bicarbonate (II.) as expressed by 

 the equation 



>N \ 



R<>>Mg-O.C' 



1>NH 



This compound (II.) cannot be imagined to be capable of 

 parting with two atoms of oxygen with regeneration of chloro- 

 phyll, so that some intramolecular rearrangement must first 

 take place, and this, according to Willstatter and Stoll, involves 

 the absorption of energy which is supplied by the sunlight. 



* Wager: "Proc. Roy. Soc.," Lond. B., 1914, 87, 386. 

 t Warner: id. 378. 



