ON EVAPORATION AND DISSOCIATION. 
Ill 
§ 65 - 
Seale readings.* 
Pressure. 
Temperature. 
millims 
O 
llo'O 
68-6 
-26 
114-9 
69-6 
-25-2 
11.3-3 
84-6 
-21-0 
112-0 
96-0 
-19-1 
112-0 
96-0 
-18-0 
111-4 
101-6 
-17-0 
108-0 
132-2 
-13-0 
106-1 
149-4 
-11*5 
106-0 
150-2 
-11-0 
105-4 
155-7 
-10-0. 
105-8 
152-0 
- 9-6 
104-7 
161-7 
- 8-7 
104-1 
167-5 
- 8-0 
100-5 
200-0 
- 5-3 
97-7 
225-3 
- 3-1 
§ 66. To obtain readings at a higher temperature, the bulb C was placed in running 
water, the temperature of which was almost constant, and mercury was removed from 
the graduated stem for convenience in reading. The readings obtained by this 
method correspond with those obtained by the still-method, to be hereafter described. 
It was accordingly assumed that they would correspond at 0°. The bulb E was 
placed in melting ice, and the position of the mercury in the graduated stem was 
noted. The ice round E was now replaced by running water at a temperature of 
13'9°, and the alteration in position of the mercury in the scale read. Since the 
temperature of the running water was not absolutely constant, this was repeated 
several tunes, and the mean result taken as correct. It was found as the mean 
of six experiments that an alteration of temperature from 0° to 13’9° produced a 
rise of mercury of 30’9 scale divisions, corresponding to an increase of pressure of 
279’3 millims. As the pressure at 0° found by the other method is 257'5 millims., 
the pressure at 13'9° is therefore 279*3257*5 = 536*8 millims. 
§ 67. A direct reading at 19'6 was taken by placing the apparatus in a large tank 
of water of that temperature, the temperature of the room being some degrees 
higher. The mercury in the scale read 81'0°. The point of the T-tube was broken, 
so as to communicate with the atmosphere, and the height of the mercury was again 
read. It was 73*2°. This difference was 7’8°, or allowing for the cooling of the 
water during one minute, 7'7°. Multiplied by 9’04, this difference is equivalent to 
69‘5 millims. Subtracting from the pressure of the atmosphere at the time, 756‘6, 
the true pressure in the apparatus was found to be 687'1 millims. 
* It should be mentioned that the scale was inverted, so that a lower reading corresponds to a higher 
pressure. 
