12 



OPENING ADDRESS 



80 



70 



60 



Q 

 \ii 

 o 50 



o 



(C 



'^ 40 



CO 



I 30 



20 



10 



I 750 LUX 



CONTROL 



©. .ALKALINE- 



\^i/ PYR06ALL0L 



PALLADIUM •- 





40 



80 120 160 



TIME (MINUTES) 



200 



240 



Fig. 2. Photolysis of water in Scenedesmus as a simple 

 manometric experiment. Hydrogen and oxygen are produced 

 in about the ratio 2:1 if photosynthesis, photoreduction and 

 phosphorylation are suppressed. Adapted algae are illumi- 

 nated in absence of CO2, under nitrogen and in presence of 

 an inhibitor of phosphorylation. The mixed character of the 

 gas evolved becomes apparent by the way it reacts after 

 the light has been turned off. 



Unless a water molecule is shown to be firmly bound as part of a 

 molecule in such a way that it is not exchangeable, metabolic reactions 

 in aqueous media will not distinguish one water molecule from another. 

 When we speak of the photolysis of water, we do not mean that the 

 emerging hydrogen and oxygen molecules stem from one and the same 

 molecule as earlier hypotheses assumed. Nobody ever suggested this 

 for electrolysis, for instance. Movements of electrons and holes, or 

 charge transfer, are part of the mechanisms of reversible oxido re- 

 ductions which in turn are the wheels of the apparatus which brings 



