152 
DE. M. 5V. TRAVEKS, MR. G. SEXIER, AXD DR. A. JAQUEROD 
tures of liquid oxygen on the hydrogen and helium scale.s. When the results were 
plotted against the absolute temperatures of water two j^arallel straiglit lines were 
obtained. From these lines the smoothed values of the ratios corresponding to those 
temperatures at which the vapour pressures of water have the values expressed in 
the following table were determined, and from them the corre.sponding teinj^eratures 
of liquid ox 3 "gen on the scale of the two thermometers were calculated (see Plate 1). 
13. The Vapour Pressures of Liquid Oxygen. 
Pre.ssures in millimetres 
of mercury. 
Temperatures on the 
hydrogen scale. 
Temperatures on the 
helium scale. i 
800 
9oh;o 
90-° 70 
790 
90-47 
90-57 
780 
90-35 
90 - 45 
770 
90-23 
90-33 
760 
90-10 
90-20 
750 
89 - 97 
90-07 
740 
89 - 85 
89 - 95 
730 
89-71 
89-81 
720 
89 - 58 
89-68 
710 
89-46 
89-56 
700 
89 - 33 
89-43 
G.50 
88-65 
88 - 75 
600 
87-91 
88-01 
550 
87-13 
87 - 23 
500 
86-29 
86-39 
450 
85-37 
85-47 
400 
84-39 
84-49 
350 
83-31 
83-41 
300 
82-09 
82-19 
250 
80-70 
80-80 
200 
79-07 
79-17 
150 
77-07 
77-17 
14. Discussion of the Pesidts. 
When the results which are tabulated in the preceeding table are plotted on a 
diagram, it will he observed that the vapour pressures of liquid oxygen on the scale 
of the two thermometers are expressed by two curves, and that the temjjerature 
corresponding to any particular pressure is always 0’1° higher on the helium scale 
than on the hjnlrogen scale. As we shall show later (Part III., p. 169), the divergence 
becomes still greater at lower temperatures. 
Though the pressure coefficients for hydrogeji and lielluin between the melting- 
point of ice and tlie Ijoiling-point of water do not appear to differ appreciablv, and 
tliough at the normal temperature these gases ma^" he considered as nearh' perfect, it 
