Vacuum microbalance Beam balance

This method is smiple but experimentally more cumbersome than the volumetric method and involves the use of a vacuum microbalance or beam balance [22], The solid is suspended from one ann of a balance and its increase in weight when adsorption occurs is measured directly. The dead space calculation is thereby avoided entirely but a buoyancy correction is required to obtain accurate data. Nowadays this method is rarely used. 

One of the classical applications of the vacuum microbalance for adsorption studies was that of Barrett, Birnie, and Cohen (32) in 1940. They measured the physical adsorption of water vapor on silica surfaces at 30°C. by direct weighing. They employed a quartz beam balance using a cemented-on tungsten wire (0.001 in. diameter) and enclosed in a high vacuum housing. The capacity of the balance was relatively high (0.5 g.)... 

Beam vacuum microbalances have greater sensitivity than hdical spring balances and the troublesome buoyancy correction at hi pressure is eliminated, at least partly if not completely. 

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