330 



JAMES H. r. SMITH 



if anv effect on the transformation. At pH 9-70, the alkahnity partly 

 inhibits the transformation and as the alkahnity is increased to 10-27, 

 ID -88, and 11-92 the inhibition is intensified. In order to estimate the 

 maximum degree of inhibition at each pH, an algebraic equation was 

 sought which permitted the limit of the transformation to be calculated 

 from the experimental data. The third order reaction velocity equation 

 did this as the concordance between experimental points, marked with 

 circles, and calculated values, depicted by solid lines, demonstrates. 



0-25 



0-20 



015 



010 



005 



000 



Equation-jY = f^^C 'C^) 



7 20 

 916 



Fk;. 3. Comparison of the rates of inactivation and limits of the transformation 

 of protochlorophyll holochrome to chlorophyll holochrome at various alkalinities. 



Between pH 9-70 and 10 -88, the limiting ^alue, 6\^„ of the chlorophyll 

 formed decreases with increase in pH. The rate constants, R, do not 

 increase markedly in this range. The amount of pigment that can be 

 inhibited from transforming at each pH, C„, increases with increase in pH. 

 It is this increase of C^, rather than the change in the velocity constant, 

 R, that causes the greater initial velocity of inhibition at higher pH. In 

 fact, the initial velocity of inhibition at 9-70, 10-27, '^^^^ 10-88 are directly 

 proportional to the hvdroxyl ion concentrations. At higher pH values the 

 increased rate of inactivation must be due to a greater velocity constant 

 rather than to an increase of inactivatible material, which has already 

 reached its limit at 10-88. 



The facts presented in Fig. 3 indicate that the inactivation reaches 

 different limits depending on pH. One interpretation of this result is that 



