114 



E. S. GUZMAN BARRON 



The speed of this catalysis was correlated to (a) the speed at which the 

 dye was reduced by the cell, and (b) the speed at which the leucodye was 

 oxidized by atmospheric oxygen. Such a correlation between free energy 

 (as determined by the oxidation-reduction potential of the dye) and rate 

 of oxidation (as determined by the increase in the O2 uptake of the cell) 

 was naturally received with caution. At the suggestion of W. Mansfield 

 Clark and with his generous cooperation these experiments were re- 

 peated in homogenous systems by studying the rate of oxidation of 

 reduced dyes by atmospheric oxygen. The same relation between free 

 energies and rates of reaction was found (4) (Fig. 2). The theory of 



Figure 2. The rate or autoxidation of reversible dyes. Abscissa, logarithm of time 



(in minutes) required to oxidize the reduced dye; ordinate, Eo — 



RT 



In 



2F I — o 



expressed in millivolts. Curve i, phenolindophenol ; Curve 2, o-cresolindo-2, 6-dichloro- 



phenol ; Curve 3, methylene blue ; Curve 4, i-naphthol-2-sulfonate-indophenol. 



absolute reaction rates, developed mainly in Princeton University by 

 Eyring and his coworkers (29, 31, 89), which focuses its attention on 

 the thermodynamic probability of molecules entering the transition 

 state, has shown that the speed of reaction depends not on the heat of 

 activation alone but also on the entropy of activation : 



KT 



k = 



-AF*/RT 



h 



where AF* is the free energy of formation of the activated state, and 

 k and h the Boltzman and Plank constants, respectively. This equation 



