ON EVAPORATION AND DISSOCIATION. 
63 
The pressure at 0° agrees very well with that given by Regnault, 184‘39 millims. 
(‘Memoires de l’Academie,’ vol. 26, 1862, p. 393) ; but at the other temperatures the 
agreement is not nearly so close. These results will be considered subsequently. 
2. Vapour-densities at Low Temperatures. 
Weight of Ether taken .—The quantity of ether taken was not determined directly 
by weighing, but was calculated from vapour-density determinations at the boiling- 
point of alcohol under atmospheric pressure. 
Series I.—Barometer, 763’1 millims. (reduced to 0°). 
Boiling-point of alcohol, 7 8'4°. 
In each set of observations the volume was altered very slightly ; in the first, for 
instance, it varied from 154 - 3 to 155'3 cub. centims., while the pressure varied from 
75 - 45 to 74 '75 millims. The number of readings and the mean values are given in 
every case. 
Number of 
readings. 
Pressure reduced to 
0°, Mean. 
Volume, Mean. 
Pressure x Volume. 
Vapour-density. 
mms. 
c.cs. 
9 
6 
5 
75-06 
85-55 
105-56 
154-77 
135-15 
110-01 
11617 "| 
11562 \ 
11613 J 
Taken as normal, 
= 37 
2 
160-85 
71-85 
11557 
37-13 
3 
438-82 
25-87 
11352 
37-80 
The mean value of p.v. calculated from the first three sets of readings is 11599*5. 
Taking the normal vapour-density of ethyl oxide as 37'0, the weight is 0‘0393 gram. 
The pressure of the saturated vapour at this temperature is nearly 3,000 mms.; and 
it will be noticed that the value of p.v. is constant, although the volume has been 
reduced from 3 to 2. 
Vapour-density at 12 - 9°.—The densities of the unsaturated and saturated vapour 
were then determined at 12'9°, the temperature being maintained constant by means 
of running water. The data follow in order. 
