540 KINETICS OF EIOLUMINESCENT REACTION. II 



Taking logarithms, 



log I = logk + log U - X) 



Substitute for log {A —X) its value from (1) 



log I = logk + log A-kt 

 or 



(2) log 7 = - ;fe^ + log Ak 



Equation 2 is the equation of a straight line, in which log / and i 

 are the two variables, and whose slope is negative and proportional 

 to the velocity constant, whose absolute value may be calculated 

 from it, as we shall see. The experimental values plot in agreement 

 with this form, and are interpreted to indicate that the luminescence 

 proceeds as a monomolecular reaction.* 



From the work of Harvey ^ and others, we can be sure that oxygen 

 is necessary to the progress of the reaction, in addition to the luciferin 

 itself. It may well be asked, therefore, why the concentration of 

 oxygen is not also a determining factor, and why it does not swing 

 the curve over in the direction of a bimolecular form. The answer 

 appears to be that under the conditions of the experiment, oxygen is 

 always present in excess, and that it therefore does not affect the 

 form of the decay curve. 



I have made it a practice to read off the slopes of the straight line 

 plottings directly from the graphical form, and have used these values 

 as if they were the velocity constants, since we are here concerned 

 with relative values, and ratios, and not absolute values. All tabu- 

 lations of relative values of k have been determined thus directly 

 from the graphs. . These values of course depend upon the choice 

 of coordinate scales. The absolute value of k may easily be calcu- 



^ In a note published from the Nela Research Laboratories (Amberson, W. R., 

 /. Franklin Inst., 1922, cxciii, 111.) I stated that the first results of the study 

 indicated a bimolecular form for the decay curve. I have since found that in the 

 first few records my photographic technique was not satisfactory for good quanti- 

 tative determinations. At the advice of Dr. L. A. Jones I adopted the develop- 

 ment technique used by the Eastman Laboratory in their method of photographic 

 photometry, and have since obtained very much better negatives which have 

 consistently indicated the monomolecular form over nearly fifty records. 



5 Harvey, E. N., Am. J. Physiol, 1920, li, 580. 



