Inventory no. 45013 - Former Display Label
GLOBES FOR WEIGHING ATMOSPHERIC AIR OR GASES
mid 19th century
Two globes, each with a brass collar and stopcock. The evacuated globe is suspended from a beam balance and weighed. The air or gas is next let in and the weight of the globe is again determined. The difference between these two measurements is the weight of the air or gas. Such globes were described by the Dutch physicist Willem's Gravesande (1688-1742) in 1721. Very accurate determinations of the density of air were made by Henri Victor Regnault (1810-1878) during the 1840's. To collect the gas, the evacuated globe was screwed into the top of a bell jar inverted in a pneumatic trough, or forming part of a gazometer. The specific gravity of the gas could be easily computed when both the weight and the volume of the gas were known.