80 
PROFESSOR W. RAMSAY AND DR, S. YOUNG 
Weight. 
Pressure. 
Volume. 
P. V. 
Vapour-density. 
1 
Percentage 
of molecules 
decomposed. 
grm. 
millims. 
cub. centime. 
per cent. 
0-01587 
113-3 
33-64 
3811 
43-08 
91-74 
107-0 
36-14 
3867 
42*46 
94-54 
102-5 
37-76 
3870 
42-42 
94-72 
The temperature was then raised to 78"2° 
•• 
119-6 
34-58 
4136 
41-87 
97-28 
The temperature was raised to 131 *8° by a jacket of chlorobenzene vapour, and two 
readings of pressure and volume were taken. From these the values of P.Y. were 
respectively 4835 and 4829 ; as it is certain that dissociation must be complete at this 
temperature, the actual weight of substance was calculated from the mean value of 
P.Y., and the number obtained was employed in the above calculation of vapour- 
densities. It is thus evident that at 60°, and at pressures near that of saturation, 
dissociation is not quite complete. In this, and in all other cases in which dissociation 
was nearly complete, a very long time elapsed before the whole of the substance had 
evaporated. 
{ OFT 
§ 20. Butyl - chloral Hydrate, C 3 H 4 C1 3 .CH 4 qjj.— This body resembles chloral 
hydrate in dissociating into butyl-chloral and water. Its vapour-density has been 
determined by Engel and Moitessier in Hofmann’s apparatus at 160°, and found to 
point to complete dissociation. It is stated by these experimenters that it begins to 
boil at 100°, and that the water distils off, leaving butyl-chloral, boiling at 165°. 
Butyl-chloral hydrate was found to separate on heating into two layers, the upper of 
which consisted mainly of butyl-chloral. A few determinations of vapour-pressures 
were made by Moitessier and Engel, and the following numbers were obtained by 
them :— 
Temperature. 
Pressure. 
O 
millims. 
16-8 
18-3 
46 - 0 
62-8 
65-0 
125-0 
78-4 
331-0 
100-0 
Over 760. 
