( 340 ) 



$ 7. Vapour pressure determination at lower temperatures. 



For these measurements 'romp. § 2 table II) die temperature was 

 directly read on the hydrogen thermometer Bur, Pt'i was used for 

 the regulation. The temperatures are - 186 3 .599 and -- 189°. 500 

 (comp. table II). At the same time we obtained a new calibration 

 for Ptj. The determinations were made with only the small vapour 

 pressure apparatus. The results are combined in table IV in the 

 same way as in table III. 



In the determinations marked {a) about halt' of the gas was con- 



4 



densed, in those marked (h) about - of the gas. As was the case 



o 



for the boiling point no systematic difference resulting from this 



seems to be perceptible. If we reduce the temperatures to the absolute 



scale and the pressures to sea-level and 45° northern latitude we 



find for : 



6 = — 186°.542 

 6 = -189°. 442 



p — 516.19 mm. 

 p — 366.24 mm. 



TABLE IV. Vapour pressure of oxygen below the boiling point. 



Date 



Pressure Mean of a Deviation 

 Time from 



in mm. series the mean 



17 Febr. 'US (a) 2 55' 366.06 



(a) 3 30 305. Do 



(b) 4 5 366.00 

 (b) 4 l 2."> 365.98 



365.99 



515.83 



§ 8. The results compared with those of other observers. 



Of previous determinations those by Travers, Senter and 

 Jaquerod 1 deserve most confidence, especially because these observers 

 used pure oxygen in a closed reservoir. This is not the case with 



'I Phil. Trans. Roy. Sue. Series A. Vol. 200. 1902 



