OF THE PABAFFINS AND THEIR MONOHALOGEN DERIVATIVES. 
25 
From the approximate equality of the densities of ethane and air the presence of 
1 per cent, of the latter makes a change of less than per cent, in the value of y, so 
that even if there were as much as 5 per cent, of air in experiments III. and IV., the 
result would be hardly affected. 
From want of experimental data I have omitted the factor 1 -f- Ijp . d [pv)ldv, but, 
as in the case of methane, it probably does not differ much from unity. 
§ 9. Ethyl Chloride. 
The material was prepared by passing hydrochloric acid into a boiling solution of 
zinc chloride in ethyl alcohol, the resulting gas being passed through water and 
sulphuric acid, and condensed in a freezing mixture. It was then redistilled, shaken 
with lime to remove hydrochloric acid which was still present, allowed to stand two 
days over calcium chloride, and again distilled through a tube of lime. 
With the vapour density apparatus that I was using at the time, tubes containing 
enough ethyl chloride to give pressures above 450 millims. would not go round the 
bend at the top. Six determinations were made at pressures ranging from 
100 millims. to 453 millims., and the rest of the curve got from the relative 
densities as given by a direct observation of the values of the product pv for a 
constant mass of the gas in the usual way. 
Fig. 10. 
A glass tube one metre long, closed at one end and graduated approximately in 
cubic centims., was carefully calibrated. 
After being filled with mercury, a little ethyl chloride was allowed to bubble up 
into it, and it was then connected at the lower end by an india-rubber tube with 
another glass tube of the same bore, and open to the air. 
MDCCCXCIV.—A. 
E 
