QUANTUM YIELD 



1957 



Absorption was determined by moving a photocell around the cuvette and 

 comparing the integral of the light transmitted and scattered in all direc- 

 tions, when the cuvette was filled with pure potassium chloride solution and 

 when it contained cells suspended in the same medium. (Within 1%, the 

 same absorptions were found when the suspension was transferred into an 



integrating sphere.) 



Fig. 



37D.29 illustrates the relation between the 



100 



^ 



3 



X 



< 



< 



q: 



\- 

 z 



UJ 



o 



>- 



CO 



< 



90 - 



80 - 



70 - 



60 - 



50 



40 



30 



20 



20 30 40 50 60 70 80 



TRANSMISSION BY INTEGRATION - % 



Fig. .37D.29. Straight-line transmission of Chlorella suspensions as function of 

 integrated transmission (straight line-transmission + scattering) (after Brackett 

 et at. 1953). 



straight-line transmission, T, and the sum of transmission and scattering, 

 T + S, for suspensions of different density. It shows that, when T is 

 30%, T + S is 70%, so that the true absorption is only 40%. This ex- 

 ample shows how erroneous absorption measurements can be on cell sus- 

 pensions in which scattering is neglected. However, the true optical 

 density (as determined by integration) was found to be proportional to the 

 apparent optical density (as determined from straight-Hne transmission), at 



