Page:Proceedings of the Royal Society of London Vol 60.djvu/169

154 (1) That the effect which ether-oxygen exerts on the viscosity of a liquid differs to a marked extent from the effect exerted either by hydroxyl-oxygen or carbonyl-oxygen, and that

(2) The viscosity of the formate is abnormally large when compared with that of other esters, and indicates that the exceptional behaviour of formic acid is to some extent retained by its ethereal salts.

Of recent years great improvements have been made in the construction of accurate thermometers. For their graduation and study, the position of the thread for at least two fixed temperatures must be known with certainty, and one of these is generally the freezing point. According to many observers, the methods at present in use for the determination of this point are unsatisfactory and cannot be relied on, even when considerable precautions are taken, to more than about 0*001° to 0*002°. The object of the present communication is to describe a method by which more consistent results can be obtained, and which is applicable to all kinds of thermometers.

The method adopted is to cool distilled water in a suitable vessel, protected from radiation, to a temperature below 0°, to insert the thermometer, and then bring about the freezing of the water by dropping in a crystal of ice. The thermometer then rises, and finally attains a steady temperature, differing only very slightly from the true zero.

Within the space allotted to this abstract, it is not possible to describe in detail all the precautions to be adopted and the apparatus employed, and for these reference must be made to the original paper. The following brief outline may, however, be given.

The apparatus consists of two portions, the thermostat and the cooler. The former is a rectangular copper vessel, filled with some liquid, which can be cooled below 0° without solidifying.

Generally either refined petroleum or a strong solution of common salt is employed. This vessel communicates by means of two wide tubes with a system of coils in the cooler, through which the liquid can be pumped by a rotary stirrer. These coils are surrounded by a freezing mixture at about —8°, and by this means the circulating liquid can be cooled and maintained for some time at about —2°. The distilled water to be frozen is contained in a tube of about 300 c.c. capacity made of clear glass. This is first placed directly