Addendum to p. 611
Recently, Warburg and Krippahl [Z. Naturforsch. 15b, 190–197 (1960)] published an experiment performed essentially with the 1951 procedure (totally absorbing suspension, two vessel method, a diffuse compensating overhead light in addition to a collimated beam). Added features of procedure were the use of a high CO2 p.p., blue-green containing diffuse light and algae grown in cyclic illumination. Since the intensity of both lights was measured actinometrically, the respective yields could be computed. These proved closely identical and ranged in both cases between 3.6 and 6.6 hv/O2 dependent upon the light intensities-three of which were used in each case. Graphical etrapolation to zero intensity brought the quantum number down to 2.7 hv/O2.