880 



as our platinum was obtained from Hkraeus like that of Pt\, \\r is 

 very probable that the temperatures as given by us are correct to 

 about 0,02°. 



IV. Detervii)iatio?i of tke end-points of condensation. 



1. Tlie apparatus. The end-points of condensation were measured 

 bj' means of a vapour-pressure apparatus provided with a stirrer, 

 as used by Kuenen. The small vessel was placed in a cryostat 

 whicli contained, beside the resistance-thermometer, a small pump 

 which provided a thorough circulation in the oxygen-bath. The tem- 

 perature was regulated by an adjustment of the pressure in the 

 cryostat. The constancy of the temperature during the measurements 

 was about 0,01^. 



2. Vapour- pressures of oxygen, nitrogen and argon. 



Beside the measurements wiiich served as a calibration of our 

 thermometer we determined the vapour-pressure of oxygen at two 

 other temperatures. 



Whereas at 83°. 5 the temperature as measured agrees with that 

 calculated from the vapour-pressure to within 0.02°, there is a 

 difference of 0.05° at 78°. It will iherefore be advisable as a 

 precaution not to use the formula for T as a function of log p for 

 purposes of extrapolation. 



