70 



PHOTOSYNTHESIS 



3600 p p \T ) 



Qy = the number of cc. of CO2, measured at the mean temperature and 

 pressure, which passes across a sq. cm. of the cross-section of the 

 tube in one hour. 

 p r= the volume of CO2 contained in unit volume of air. 

 L = the length of the tube in centims. 

 T° = the zero of absolute temperature. 

 T = the mean temperature during the experiment, expressed on the abso^ 



lute scale, 

 p =r the mean barometric pressure in millims. of mercury." 



TABLE 11 

 Results of Brown and Escombe on the Rate of Diffusion of Carbon Dioxide. 



CO2 



Diffused 



per Sq. 



Cm. per 



Hour 

 Measured Mean 



at Temp. COa 



Duration Total and Pres- Mean Content 



of Ex- Length CO2 sure of Tempera- of Air 



periment of Tube Diam. Diffused Experi- ture Mean 



in in Cm. Cc.atO°, ment Barom- Parts per 



Hours Corrected Cm. 760 Mm. Qvt. ° C. eter 10,000 K° 



500.9 18.0 2.32 23.89 .01175 7.7 751.2 3.70 .151 



501.0 75.0 2.32 6.33 .00311 7.7 751.2 3.70 .167 



501.0 18.0 2.32 20.88 .01036 9.1 763.4 3.61 .133 



384.0 20.1 2.28 14.91 .00989 13.3 766.3 3.39 .146 



383.7 19.9 2.30 15.49 .01260 13.3 766.3 3.39 .185 



384.8 36.6 2.23 8.81 .00609 13.3 766.3 3.39 .164 

 386.4 37.3 2.20 7.91 .00559 13.3 766.3 3.39 .154 



Mean K° 157 



The mean value for K° of all their experiments was 0.158. Below 



are given the values obtained by other investigators for the interdiffusivity 



of carbon dioxide and air with higher partial pressures of the former 



gas apd with both gases at the same pressure. 



K° 



Loschmidt " 142 



von Obcrmayer '* 132 



Waitz " 151-.158 



Waitz, recalculated by von Obermayer for dry gases 131-137 



Brown and Escombe calculated that their results are but very slightly 

 afifected by the presence of water vapor in the air through which the 

 carbon dioxide was passing. 



"Loschmidt, IVien. Akad. Ber., 61 (2), 62, 367, 468 (1870). 



"Von Obermayer, ibid., 85 (2), 147, 748; 87 (2), 188; 81, 1102 (1880). 



"Waitz, Ann. Phys. Chem., 17, 201 (1882). See also Meyer, O. E., Kinetic 

 Theory of Gases, Eng. translation, p. 267 (1899). Stefan, IVieti. Akad. Ber. 83 

 (2), 613 (1881); 79 (2), 161; 78 (2), 161 (1877). 



