524 





M 



r. E 



. C. C. Baly 



on the 



Temperati 





Ratio in Vapour. 



Eatio in Vapour, j 



jre. 





Observed. 





Calculated. 



o 



79 







073 





•072 



80 







•136 





137 



81 







•215 





•215 



82 







•309 





•310 



83 







•428 





•432 



84 







•584 





•586 



85 







•794 





•795 



86 







109 





109 



87 







1-53 





1-55 



88 







2-29 





2-30 



89 







3-87 





3-87 



90 







881 





8-87 



and helium thermometers, and by Estreicher* on the satura- 

 tion pressures of oxygen. Olszewski's measurements were 

 five in number, and the means from the two thermometers 

 were as follows : — 



Pressure. Temperature abs. 



741 mm. 90*35 



240 „ 81-15 



90-4 „ 74-25 



12-0 „ 63-75 



90 ,. 62-32 



In order to complete the vapour-pressure curve for the 

 above, the ratios of the temperatures giving equal vapour- 

 pressures with water and oxygen were plotted against the 

 water temperatures according to Ramsay and Young's equa- 

 tion!. The vapour-pressures of water were taken from 

 Regnault's values as corrected hj Broch. From the straight 

 line passing through the points, data were calculated for the 

 vapour-pressure curve. This was drawn, and gave the 

 boiling-point at 760 mm. as 90 o, 60 absolute. 



As regards Estreicher's measurements, of which there are 

 44, they have been plotted directly, but it is difficult to draw 

 a curve through them for they are very scattered at the 

 higher temperatures. The point he gives as the mean of 

 25 observations, P = 743*8 mm. T = 90°'44, agrees very well 

 with Olszewski's values, and so do two more points. If, then, 

 these points be taken as correct and the curve drawn, this 

 can only be done by neglecting entirely many points at 

 medium pressures. The curve, then, is almost superposed on 



* Phil. Mag. (5) xl. p. 454. 



t Ibid. (5) xx. p. 515, xxi. pp. 33, 135. 



