ox THE MEASUREMENT OF TEMPERATURF. 
185 
PART II. 
On the Vapour Pressures of Liquid Oxygen at Temperatures below its Boiling-Point 
on the Constant- Volume Hydrogen and Helium Scales. 
By Morris W. Travers, D.Sc., Felloiv of University College, London, 
George Senter, B.Sc., aud Adrien Jaquerod, D.Sc. 
C'ONTEXTS. 
Page 
1. Introduction. 13;') 
2. Previous measurements of the A’apour pressures of liquid oxygen. I;!() 
3. The pressure coefficients of hydrogen and helium hetween 0“ and 100 ( '. 138 
. 4. The coefficient of expansion of glass between 16’ and - 190’ C.1 38 
5. Method of experiment.. 138 
6. The large constant-volume thermometer. 138 
7. The smaller constant-volume thermometers. I ll 
8. Calibration of the thermometers. 143 
9. Calculation of the results. 1 |o 
10. The vapour pressures rjf liquid oxygen on the constant-volume hydrogen scale . . . l lo 
11. The vapour pressures of liquid oxygen on the constant-vcjlume helium scale . . . . 118 
12. Treatment of the results. Ibl 
13. Taladated vapour j^ressures of liquid oxygen. 1.32 
14. Discussion of the results. 1.32 
15. The probable accuracy of the results. 15;; 
1. hitroditctioii. 
After detei'miiiiug the pressure coefficients of hydrogen and helluni hetween the 
nielting-])oint of ice and the boiling-point of water, and so obtaining tlie fundamental 
intervals of our thermometer scales, we proceeded to apply our residts to the 
determination of the boiling-point and vapour pressures of liquid oxygen. In these 
experiments we have employed three different thermometers; the coefficient of 
expansion of the glass at low temperatures has been specially determined; every 
precaution has been taken in preparing the different samples of hydrogen and helium 
employed; and the errors clue to impurity in the oxygen and to the superheating of 
the licjuid have, Ave believe, been eliminated. The following account contains full 
details of our experimental method and i-esidts. 
