A handbook of laboratory glass-blowing by Bolas Bernard D

Author:Bolas, Bernard D
Language: eng
Format: epub, pdf
Tags: Glass blowing and working
Publisher: London, G. Routledge & sons, ltd.; New York, E. P. Dutton & co.
Published: 1921-03-25T05:00:00+00:00

LABORATORY GLASS-BLOWING 57

Combustion-Glass. — Is usually a glass containing more calcium silicate and potassium silicate than the ordinary "soft" soda-glass. It is much less fusible than ordinary soda-glass, and passes through a longer intermediate or viscous stage when heated. Such a glass is not very suitable for use with the blowpipe owing to the difficulty experienced in obtaining a sufficiently high temperature. If, however, a certain amount of oxygen is mixed with the air used in producing the blowpipe flame this difficulty is minimised.

Resistance-Glass. —May contain zinc, magnesium, and other substances. As a rule it is harder than ordinary soda-glass, and less suitable for working in the blowpipe flame. It should have very little tendency to dissolve in water, and hence is used when traces of alkali or silicates would prove injurious in the solutions for which the glass vessels are to be used.

Lead-Glass. —This, or " flint" glass as it is often called from the fact that silica in the form of crushed and calcined flint was often used in making the English lead-glasses, contains a considerable proportion of lead silicate. Such

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