1909-10.] Vapour Pressures of Solids and Liquids. 
523 
XXXVIII. — A Static Method for Determining the Vapour Pressures 
of Solids and Liquids. By Alexander Smith and Alan W. C. 
Menzies. 
(MS. received June 7, 1910. Bead July 4, 1910.) 
The apparatus to be described was developed from the submerged bulblet 
apparatus, a description of which was recently published in these Proceed- 
ings (vol. xxx. p. 437). 
The Isoteniscope, Bath, and Stirrer. — The substance is placed in the 
spherical bulb (20 mm. in diameter). The confining fluid, which, when a 
liquid is being investigated, is the same material as the substance, occupies 
the lower part of the U-tube (fig. 1). The whole instrument, which we 
have called the Static Isoteniscope, is 24 cm. long. It is suspended, along 
with the thermometer and mechanical stirrer, in a tall 2-litre beaker, con- 
taining a suitable bath liquid. When the substance is a solid, then the 
U-tube is charged with mercury, melted paraffin, a fusible alloy, or a 
molten salt or mixture of salts. To secure steadiness and equal distribution 
of temperature, a cylindrical glass screen (cut from a broken beaker) sur- 
rounds the bath, and a very active stirring arrangement is used. 
Measurement of Temperature and Pressure. — In the work to be 
described, a platinum resistance thermometer, adjusted and standardised so 
as to give the absolute temperature with an error of less than d= 0 o, 01 below 
100°, and of less than ± 0°T up to 450°, was employed. The fixed points 
were 0°, 100°, and the boiling-point of sulphur (taken to be 445°), and the 
thermodynamic scale was used. The fixed points were redetermined at 
frequent intervals during the work. 
The gauge was read by means of a hairline ruled on a strip of glass 
travelling on a cursor. A mirror behind the gauge eliminated the effects of 
parallax. For the reduction of the readings to mercury height at 0°, five 
thermometers, suspended at intervals beside the gauge, were employed. 
Correction was made for the coefficient of expansion of the previously 
calibrated scale (a steel tape), and for the local value of the gravity 
constant. 
The Manipulation. — Fig. 2 shows diagrammatically the arrangement 
of the rest of the apparatus. The isoteniscope and gauge were connected 
with a large iron bottle. This, in turn, could be put into communication 
