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Abstract

A process of manufacturing vitreous beads is disclosed in which feedstock particles of a glass-former composition containing chemically bound water, are fed through a heating zone in which the particles are vitrified and spherulized and the resulting vitreous beads are cooled. The size of the feedstock particles and their content of substance which becomes gaseous during the passage of the particles through said heating zone are such that a least 20% by weight of the formed beads have a relative density greater than I.O. The vitrifiable oxide forming elements of said glass-former composition may be chemically interlinked, and the feedstock may be prepared as a silica-based gel or precipitate having a composition suitable for vitrification into a glass of any desired composition for example one which by virtue of its low alkali content is resistant to hydrolytic attack. By control of the cellulating agent content (bound water and optionally a gas evolving salt radical such as nitrate or sulphate) of the feedstock, and its granulometry, the relative proportions of solid and hollow beads which will be produced in a given spherulizing run can be controlled.

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First Claim