THE VISUAL PIGMENTS 



plotted against t) while in (7), the coefficient of t includes (f> which 

 contains the variable 7^. 



This apparent contradiction is resolved by the fact that <^, though 

 a variable, changes very little in any one experiment. This is illus- 



oo 2-0 

 \/ 1-0 



Optical density 

 0-5 0-4 0-3 0-2 0-1 



1-00 — 



0-95 — 



0-90 — 



0-85 



0-80 



0-75 — 



0-70 — 



10 20 30 40 50 60 70 80 90 100 

 Percentage transmissivity 



Fig. 3.5. The variation of (f> with the percentage transmissivity of bleach- 

 ing solutions having various final transmissivity values from 1-0 to 0-5, 

 as indicated. The full line portions of the curves apply to solutions 

 which decrease, and the dotted to those which increase in transmissivity 

 as they bleach. 



72 



