88 PROFESSOR W. RAMSAY AND DR. S. YOUNG- 
for on lowering the temperature the pressure of the bromonaphthalene vapour, after 
the pressure of mercury-vapour had been subtracted, was found to be the same as that 
under which the bromonaphthalene which jacketed the tube, was boiling. The 
detailed results are as follows:— 
Temperature. 
Pressure of 
bromonaphthalene 
in jacket. 
Total pressure 
in 
barometer-tube. 
Vapour-pressure 
of mercury. 
A. 
Corrected to 0°. 
O 
millims. 
millims. 
millims. 
mi lims. 
238-2 
290-6 
346-7 
55"5 
291-2 
290-1 
(54-1)* 
292-6 
291-5 
The level of the mercury was fluctuating about 1 millim. 
It is thus seen that the combined vapour-pressure of these two substances is equal 
to the sum of the two vapour-pressures taken separately. 
§ 37. A. fresh tube was boiled out, and ammonium chloride was introduced. On 
heating with vapours of different liquids under different pressures the following 
results were obtained :— 
Temperature. 
Pressure. 
Duration of experiment. 
O 
millims. 
98-2 
0-2 
Constant 
122-9 
3-5 
23’ 
132-0 
3-9 
10' 
140-9 
4-3 
Constant 
151-9 
4-7 
7' 
165 9 
4-9 
8' 
183-3 
5'5 
34' 
200-0 
9-1 
36' 
210-1 
12-3 
60' 
223-0 
18-1 
32' 
241-9 
32-1 
29' 
251-4 
48 8 
43' 
261-3 
72-5 
65’ 
2711 
99-4 
11' 
280-7 
144-4 
? 
The last observation admitted of no regular time-curve, on account of the difficulty of 
forcing up the vapour. A constant result w r as finally obtained at the pressure given. 
§ 38. After cooling, a permanent gas remained, exerting a pressure of 50 ‘2 millims. 
This after two days had fallen to 44 millims. The tube was then inverted, which 
removed some of the gas, and after being placed in position, was again heated. The 
atmospheric pressure was 760 millims., hence the boiling-point of bromonaphthalene 
was 280‘3 o . The pressure now rose to 145‘9 millims., almost identical with the former 
reading. After again cooling, the pressure was 35 millims. On introducing water, a 
portion, at least, of the permanent gas was dissolved. As the pressure thus obtained 
w r as identical within limits of error of experiment with that yielded by the still- 
* From our table. 
