1903.] Measurement of il\e Pressure Coefficient of Oxygen. :.S5 



Taking SQ = 1*98 c.c. at 50 C., which is obtained by interpolating 

 between and 100 C., on the assumption that the cooling effect varies 

 inversely as the square of the absolute temperature, and taking the 

 mean of the results so obtained; taking K = 2 '59 x 10 6 , and p (the 

 pressure at 50C.) = 81 cm. mercury = 1-08 x 10 (CGS), we have from 

 equation (1) T = 0*913. Hence since the scale correction at 50 C. 

 maybe neglected in comparison with the zero correction, - T = 0'913. 



Now the pressure coefficient, as determined above, at an initial 

 pressure of 70 cm. of mercury is 0-003674, whence 



TA - - >7 i >'18 



~ 0^003674" 



#o is thus equal to 273'09, a result which is in good agreement with 

 the value of the same quantity obtained by Callendar* for air, 

 nitrogen, and hydrogen. 



It will be observed by reference to equation (5) that d (pv)/dp 

 changes sign at a temperature 23 C., at the pressure employed in the 

 above experiments. 



In conclusion we desire to express our very best thanks to 

 Dr. Travers, not only for his kindness in putting his apparatus at our 

 disposal, but also for the unfailing interest which he has shown in the 

 progress of the work. 



* Loc. dt. 



VOL. LXXII. 2 E 



