The effect of base-metal impurities on the surface tension of mercury

Abstract

The surface tension of mercury in air has been found, by the drop-weight method, to be 476.0 ± 2.0 dynes/cm at 25°C. The values of the surface tensions of seven different grades of mercury, which varied from commercial to polarographic, were measured and found to have the same values (within experimental error). The sample grades were analyzed and were found to contain very similar base metal impurity levels, i.e., <2 ppm of mercury. The “dulling” of mercury, and its “tailing” on glass surfaces in air is apparently due to the formation of base-metal oxides. Even very pure mercury exposed to dry air (uncontaminated) will gradually “dull,” and “tail” on glass, after long exposure times. However, when mercury surfaces are kept in vacuo, or in an inert gas, they retain their metallic lustre indefinitely. It is possible that base-metal impurities as high as 5–10 ppm of mercury can be tolerated if the mercury surface is kept in vacuo, or in an inert gas.