CHANGE FROM THE LIQUID TO THE SOLID STATE ON VAPOUR-PRESSURE. 473 
Temperature. 
Difference between A an<l B. 
Correction for B. 
O 
O 
O 
0 
032 
021 
-1 
0-34 
0'23 
— 2 
0-37 
0'26 
-3 
0-40 
0-29 
-4 
0-42 
0'31 
— 5 
O'45 
0'34 
31. A comparison of thermometers A and C was made before and after the experi¬ 
ments. They were first placed in melting ice, when A read 0 o, 18 and C, which had 
been altered in order to secure greater range, 7°‘65. In vacuo the zero-points of 
these thermometers were 0°T1 and 7°'10 respectively. Thus thermometer A fell 
0 o- 07, while C fell 0 o, 55, the difference being 0 o, 48. This was repeated after the 
experiments described in Series II., when A placed in melting ice read 0 o- 23, and 0 
7°‘72, and in vacuo 0°'17 and 7°T 3 respectively. Thus A fell 0 o, 06 and B 0°‘59, the 
difference being 0°'53. This agrees with the comparison of the two thermometers at 
the atmospheric pressure and in a vacuum. At the same time, other readings of 
thermometer C were somewhat variable, and it was therefore deemed advisable to 
assume that the zero-point of C in Series II. was 7°'23. That this is so is shown by 
the fact that, taking this number as correct, the differences between the two thermo¬ 
meters disappeared at 0°. But even if 7°T3 were accepted as the zero-point of C it 
would not materially affect our results. 
32. The experiments were conducted in the following manner:-—-Water was admitted 
so as to moisten the cotton-wool of both thermometers. Air was then removed as far 
as possible by means of the Caere pump ; it was then disconnected. The condenser 
was next cooled, when the temperature registered by both thermometers quickly fell 
to about —5°. Solidification then took place, the temperatures rapidly rising to 0 C , 
and quickly falling again. The freezing-mixture was then removed, and a little 
air introduced, and one tube was jacketed with hot water. Both thermometers 
remained stationary at 0° for some time ; the one which was warmed was allowed to 
rise to about +15°; the other thermometer remained below +3°. The freezing- 
mixture was then replaced, and air was slowly removed by the Sprengel pump. 
Under these circumstances it invariably happened that ice was formed on that 
thermometer, the temperature of which had not risen above 3°, as soon as the pressure 
fell below 4'6 millims., while the water on the other thermometer could be cooled to 
— 5 without freezing by slowly reducing pressure. At a temperature between —5° 
and —6° it always froze. Between —5° and —0°, therefore, it was possible to obtain 
comparative readings. 
33. In the tables which follow all the readings are given, except some preliminary 
ones made before the method of manipulation had been learned. 
3 p 
MDCCCLXXXJV. 
