Surface Tension of Mercury in the Presence of Gas Under Varying Pressures

Abstract

Quincke's method with Worthington's correction was used. Contrary to the accepted values the maximum surface tension of mercury (515±7 dynes/cm at 31°C) is reached when only mercury vapor is present. A surface freshly created in a gas at 760 mm has a high initial tension approaching that when the surface is created in mercury vapor. The tension falls as the gas is adsorbed until an equilibrium value for a given pressure is attained. As the pressure is reduced the equilibrium value rises to a maximum which depends upon the nature of the gas. For instance, this maximum tension for mercury-hydrogen occurs at the critical pressure of 2.8 mm. If the pressure is lowered to stiction the tension remains unchanged so long as the mercury is not agitated beyond a certain amount. This maximum value for mercury-hydrogen is 441 dynes/cm which is less than the mercury-mercury vapor value of 515 dynes/cm. If the mercury-hydrogen is violently agitated when the pressure has been reduced to stiction the tension approaches 515 dynes/cm, the mercury-mercury vapor tension. Vibrating drop methods tend to give the vacuum value of the surface tension even when a gas is present at atmospheric pressure.