DESIGN AND PERFORMANCE OF A FUSED SILICA MICROBALANCE

Abstract

The construction and the use of a robust microbalance with a fused silica beam are described. The design is such that the microbalance is undisturbed by convection even in surroundings where it would be impossible to use an ordinary microbalance; nevertheless the instrument is very convenient to operate. A comprehensive theoretical treatment of the silica torsion balance and of the effects of constructional imperfections is given and shown to be in good agreement with experiment. The performance of the microbalance is illustrated by means of an example from the microchemical work of B. G. Harvey, where four samples of americium oxide, of masses between two and six micrograms, were weighed on 100 mgm. scale pans, with a proven accuracy better than 0.3%. The precautions that were taken to minimize the harmful effects of adsorption and dust are described. A commercial version of this microbalance is now available.