INHOMOGENEITY OP LIGHT ABSORPTION 



1009 



p/pmax. ^ j^js^^ q£ ^^^.q chlorella suspensions of different density {cf. Table 

 25.1) given b}^ Eichhoff (1939). Their relationship is in agreement with 

 the prototype of figure 28.20 (curve 5). Katz, Wassink and Dorrestein 

 (1942) attempted to reduce analytically the Ught curves obtained with 

 three suspensions of bacteria (Chromatium, D) of different concentration 

 to a single curve showing the average yield per cell as function of average 

 iUumiiiation. In a 2 cm. deep absorption vessel, the "dense" suspension, 



0.8 - 



Q. 



2 4 6 



LIGHT INTENSITY 



Fig. 28.21. Light curves of a thin and a dense Chlorella 

 suspension, in red hght, X = 6500 A (after Eichhoff 1939). 

 Intensity in "energetic meter candles" (HK) (page 1098). 



with a concentration of 30 "Trommsdorff units"/ml. (concentration 3) 

 absorbed about 80% of incident light of a sodium lamp, the "medium" 

 suspension (concentration 1; 10 Trommsdorff units), about 60%, and the 

 "thin" suspension (concentration \; 2>\ units), about 30%. Figure 28.22A 

 shows the empirical light curves of these three suspensions, P = f{I)- They 

 have the relative positions anticipated in figure 28.20 {!) (except for the 

 sigmoid initial shape, which is characteristic of the Hght curves of purple 

 bacteria). 



Near 7 = 0, the order of the three curves is reversed. The probable reason for this 

 is that, at a given incident light intensity, the average illumination is lowest in the densest 

 suspension; therefore, the deficiency of hydrogen consumption (which we think, is re- 

 sponsible for the sigmoid shape) is maintained, in the dense suspension, up to higher in- 

 tensities than in the dilute one, and tliis influence apparently overcompensates that of 

 stronger absorption. 



