1896-97.] Prof. J. P. Kuenen on Ethane and Butane. 
433 
On Ethane prepared from Ethyl Iodide, and on the Pro- 
perties of some Mixtures of Ethane and Butane. 
By Professor J. P. Kuenen. (With Three Plates.) 
(Read April 5, 1897.) 
In a paper on mixtures of ethane and nitrous oxide, read before 
the Physical Society of London in May 1895,* I communicated a 
set of observations with regard to the condensation and the critical 
state of ethane. This substance was prepared by electrolysing 
sodium acetate : it was purified with fuming sulphuric acid, caustic 
soda, and phosphorus pentoxide, and condensed in a small copper 
cylinder, where it was subsequently boiled at low temperature in 
order to expel all permanent gas. The ethane with which the 
glass compression-tubes were filled was drawn from the liquid con- 
tained in the copper cylinder. Its condensation-pressures and 
critical constants are contained in the following table, which is 
taken from the paper mentioned (comp. fig. 3) : — 
t. 
5-85 
H)*65 
15*4 
22-4 
29*35 
31*0 
32*0 
Table I. — Ethane. 
p. 
. 27*4 
. 30*45 
. 33*8 
. 39*7 
. 45*9 
. 47*6 
. 48*8 Critical point. 
The values of p and of the critical constants in Table I. are not 
absolutely correct. The observations showed the substance to 
contain some impurity, the condensation-pressures not being quite 
constant, but showing a slight increase, as is always the case for 
mixtures. The difference of the pressure at the beginning and at 
the end of the condensation amounted to 0*43 atmospheres at 
15° C. It is, however, unlikely that this impurity in the ethane 
can have affected the values for p by more than a few tenths of 
* Phil. Mag., 40, pp. 173-194. 
