432 Proceedings of the Royal Society of Edinburgh. [Sess. 
XXVI— A Method for determining Boiling-Points under Constant 
Conditions. By Alexander Smith and Alan W. C. Menzies. 
(MS. received April 13, 1910. Read May 16, 1910.) 
(Abstract.) 
A method for determining the boiling-points of solids as well as liquids, 
such that little material is required, and only constant, easily reproducible 
conditions are involved, is much needed. None of these qualities is 
possessed by the distilling flask method. 
The apparatus suggested consists of a bulblet with a bent capillary not 
less than 1 mm. in diameter. This is attached to a thermometer and 
suspended in a beaker (flg. 1). The latter contains water (for substances 
boiling below 100°), sulphuric acid (up to 200°), melted paraffin (up to 280°), 
or a mixture of sodium and potassium nitrates (45'5, 545 parts) for use 
from 220° upwards. A stirrer is provided. 
After charging (with 0'03-01 g. of the substance), attachment, and 
submergence of the bulblet, the bath is heated. When the temperature 
has remained at the boiling-point for a few moments, dissolved and occluded 
gases and moisture have all been expelled, and a rapid stream of pure 
vapour issues. In case the substance is insoluble in the bath-liquid, the 
bubbles of vapour rise to the surface. With falling temperature and 
vigorous stirring, the point at which the bubbles suddenly cease can be 
read accurately: this is the boiling-point. In contrary case of mutual 
solubility of the substance and bath-liquid, the point at which boiling 
ceases cannot be ascertained sharply. Here the bath-liquid is allowed to 
recede into the capillary to a point 5-10 mm. from the opening, opposite to 
some mark on the thermometer or binding thread. The temperature at 
which this point is reached is the boiling-point. 
The vapour pressure of the bath-liquid has no influence on the result, 
and chemical interaction of the substance and bath-liquid will not usually 
interfere with the observation. 
The expulsion of foreign gases and vapours is repeated until constant 
values are obtained, or the impurity of the substance has been demonstrated 
by the absence of a constant boiling-point. 
As in all boiling-point observations, the barometric height (at 0°) must 
be recorded. A correction for the head of liquid above the opening of the 
