A densitometer to be used for liquids at temperatures up to ca. 1000°C and maintained in an inert atmosphere was constructed. The hydrostatic weighing method of Kohlrausch was chosen as the method most readily adaptable to the conditions imposed. This method utilises the buoyancy principle of Archimedes. The plummet was suspended from one arm of an analytical balance and immersed in the sample contained in the densitometer tube. The apparent loss in weight of the plummet upon immersion was measured by a chainomatic balance. The entire apparatus was made gas-tight; observations and manipulations of the balance were made through gas-tight seals.