XXXVIII.—A Static Method for Determining the Vapour Pressures of Solids and Liquids

Extract

The apparatus to be described was developed from the submerged bulblet apparatus, a description of which was recently published in these Proceedings (vol. xxx. p. 487).

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 ∪-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, containing a suitable bath liquid. When the substance is a solid, then the ∪-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) surrounds the bath, and a very active stirring arrangement is used.