434 Proceedings of Royal Society of Edinburgh. [sess.. 
an atmosphere. Nor will the value for the critical temperature- 
differ hy more than 0'1 or O^ 0 C. from the true value, consider- 
ing that Andrews’ carbonic acid showed changes in vapour-pres- 
sure of over two atmospheres under 'the same circumstances, and 
that his value for the critical temperature, 30 '9° C., is only about 
0* * * § 4° C. too low. 
The values obtained by others for the vapour-pressures, and 
especially for the critical constants, differ materially from mine. 
Dewar * gives 35° C. for the critical temperature, Olszewski f 
34° C. and 50 '2 atmospheres for the critical pressure, Haenlen j 
from 32°-40°, probably 34 - 5° C. and 50 atmospheres. The 
vapour-pressures obtained by Olszewski and Haenlen are given 
in Table II. 
Table II. — Ethane. 
1. Olszewski. 
t. 
P- 
-93 
1 
+ 0 
23*8 
+ 23-5 
40-4 
+ 29 
467 
+ 34 
50 ‘2 Critical point. 
2. Haenlen. 
t. 
-31 
-20 
-11 
+ 0 
+ 15 
+ 34-5 
V • 
11 
14-5 
18-3 
23-3 
32-3 
50 Critical point. 
Haenlen’s values are constantly a little lower than mine ; 
Olszewski’s, at higher temperatures, a little higher. Olszewski 
prepared his ethane from (C. 2 H 5 ) 2 Zn, Haenlen from ethyl iodide by 
the method of Gladstone and Tribe, as applied hy Frankland.§ 
As I was desirous to ascertain the reason for the discrepancy 
between the different results, I prepared some ethane hy Frank- 
land’s method, and the results are contained in this paper. The 
gas passed through a “scrubber,” fuming sulphuric acid, bromine 
and caustic potash, was collected in a gasometer, dried with lime 
and phosphorus-pentoxide, and compressed || into a copper cylinder 
similar to the one used by me on former occasions. 
* Phil. Mag. (5), 18, p. 214. 
f Bulletin Ac. des Sciences de Cracovie, 1889, p. 27. 
J Liebig's Annalen, 282, p. 245. 
§ Jour. Chem. Soc., 45, p. 154 ; 47, p. 236. 
|| The compression-pump was a Natterer, which was very kindly lent to mo 
by Prof. Crum-Brown. 
