m THE PRESENCE OF DUST-FREE AIR AND OTHER OASES. 
287 
Oxygen. 
Preparation .—Potassium permanganate v/as heated in a small glass tube fused on 
to H (fig. 2). This was exhausted and then heated till the pressure considerably 
exceeded that of the atmosphere, and the process of alternate exhaustion and heating 
many times repeated. 
The mercury reservoirs B, with the taps Tj, Tg served as a pump. 
Results .—Oxygen behaves exactly like air in these experiments. The expansion 
required to produce both rain-like and cloud-like condensation, is practically the same 
in both. The colour phenomena are also exactly alike. 
Expansion required to produce Rain-like Condensation in Saturated Oxygen. 
Pressures all given in millimetres of mercury. Correction for piston weight, 
IV = 1 millim. 
Date. 
1 
B. 
f C. 
IT. 
Pv 
Pu 
Pi- 
Ps- 
Pi/Pj = 
May 8. 
769 
17 
14 
594 
1348 
318 
1072 
1'258 
; „ 14 . 
768 
20 
17 
638 
1388 
357 
1107 
1-2.54 
; „ 15 . 
i 
1 
768 
21 
18 
579 
1328 
307 
1056 
1-258 ! 
i 
Mean 
1-257 
A fresh supply of oxygen was used eacli day. 
Expansion required to produce Cloud-like Condensation in Oxygen. 
Date. 
B. 
f C. 
'TT. 
Pv 
P 
Pi- 
Ps- 
P1/P2 — ^2/D- 
May 9 . . . . 
769 
18-0 
15 
732 
1485 
318 
1071 
1-386 
1 
„ 14 .... 
767 
20-5 
18 
659 
1407 
273 
1021 
1-378 
2 
„ 14 . . . . 
766 
21-5 
19 
665 
1411 
273 
1019 
1-.385 
Mean 
1-383 
Measurements vrere also made of the ratio when the colour produced by the 
expansion was the sensitive tint between the blue and red referred to in the account 
of the colour phenomena observed in the experiments with air. 
