QUANTUM YIELD 



1941 



labelled carbon dioxide in the dark, the "carbon dioxide reservoir" from 

 which the burst originates, was found to be tagged within a couple of 

 minutes — even more rapidly than this reservoir is refilled after it had been 

 emptied in light (a "pick-up" which has a half-time of about 5 minutes). 

 It is unexpected for an isotopic COi-exchange — presumably, RC(12)00H 

 -t- C(13)02 ;^ RC(13)00H + C(12)02, where R is an organic radical— to 

 be more rapid than the carhoxijlation RH -|- CO2 -> RCOOH ! 



Cyanide was found to affect the burst more strongly than photosynthe- 

 sis; the inverse relation prevailed with o-phenanthroUne. 



(a) Experiments by Warburg and Co-workers since 1950 



The studies of Warburg, Burk and co-workers, carried out in Germany 

 after 1950, were mentioned only in a footnote in chapter 29 (p. 1113), 

 and require more detailed presentation here. 



Approach to Perfect Energy Conversion Yield. Warburg, Burk and 

 Schade (1951) described improvements in the previously employed tech- 

 nique. A divided beam was used to illuminate the two reaction vessels 



Cell-suspension 



Actinometric liquid 



I i 



-Light beam 



Fig. 37D.24. Actinometric vessel for measuring light transmission of 

 cell suspensions (Warburg, Burk and Schade 1951). 



equally and simultaneously, thus avoiding errors caused by differences in 

 the time and order of treatments of the cells in the two vessels. Mixing 

 was further accelerated (to 220 swings per minute) ; the vessel volume was 

 increased (from 13 and 20 ml. to 20 and 30 ml., respectively) so that the 

 smaller, as well as the larger, vessel provided adequate space for circulation 

 of the liquid (7 ml.). Respiration was compensated by white light; 

 it was beheved that this reduces the uncertainty of the respiratory correc- 

 tion, because the respiratory state of cells maintained near compensation 



