228 LORD RAYLEIGH AND PROFESSOR W. RAMSAY ON ARGON, 
13. Behaviour at Low Temperatures. 
A single experiment was made with an early sample of gas, of density 19°1, 
which certainly contained a considerable amount of nitrogen. On compressing it in a 
pressure apparatus to between 80 and 100 atmospheres pressure, and cooling to 
— 90° by means of boiling nitrous oxide, no appearance of liquefaction could be 
observed. As the critical pressure was not likely to be so high as the pressure to 
which it had been exposed, the non-liquefaction was ascribed to insufficient cooling. 
This supposition turned out to be correct. For, on sending a sample to Professor 
OLSZEWSKI, the author of most of the accurate measurements of the constants of 
gases at low temperatures, he was kind enough to submit it to examination. His 
results are published elsewhere ; but, for convenience of reference, his tables, showing 
vapour-pressures, and giving a comparison between the constants of argon and those 
of other gases, are here reproduced. 
‘VV APOUR-PRESSURES. 












| | | ] 
| ae | Pressure. Temperature. | Pressure. Temperature. | Pressure. 
| : | cs | ae oe f i = 
| — 186-9 740°5 millims. — 136-2 | 27:3 atms. — 1294 | 35°8 atms. 
| 
Pies 139'1 23:7 atms, | — 1351] 290 ,, —1286 | 3280 ,, 
| 1383 25:3 55 — 1344 HS} on — 121-0 | BOO 5, 
| | | | 
| Critical | | ong a el . Pens Col 
Gast | ornare | Critical | Boiling- Freezing- | Freezing Density | of liquid olour of 
P pressure. | point. point. pressure. | of gas. | at boiling- liquid. 
| BEE | point. 
| : 
| atms. 6 > | millims. | | 
Hydrogen, H, . . .| Below | 20:0 ? ? || 1 P Colourless 
| —220:0° | 
Nitrogen, N,. . . .|—146:0) 35:0 —1944 —214:0 60) 7 |) 4 0;885e 3 
Carbon monoxide, CO | —139°5 35°5 — 190-0 | —207-0 100 era ? 3 
Argon yAT elroy fale be | al 210 ne o0;695i 186,95 89:65 ae | 19:9 | About és 
| | cd | 
Oxygen, O, . . .{—1188 | 50°8 --182°7 ? ? Ks) 1124 Bluish 
Nitric oxide, NO > 6) Ger) cilky —153°6 | —167°0 133 eeerlomes| Pp | Colourless | 
Methane, CH, Pes — S38 549 | —1640 | —185°8 | 80 | 8 0°415 _ 
| | | | 



14. The ratio of the Specific Heats of Argon.* 
In order to decide regarding the elementary or compound nature of argon, 
experiments were made on the velocity of sound in it. It will be remembered that 
from the velocity of sound, the ratio of the specific heat at constant pressure to that 
at constant volume can be deduced by means of the equation 
* See Addendum, p. 239. 
