Crucible
Historical document, translated for reference. It reflects medical knowledge of the 1920s–30s and is not medical advice.
Summary
This article describes the various materials used to manufacture crucibles for high-temperature melting, including metals, porcelain, and graphite. It also provides practical guidance on the care and limitations of platinum crucibles in laboratory settings.
Encyclopedia article (1928–1936)
CRUCIBLE is used for melting substances at high temperatures. Crucibles are available for sale in metal (iron, copper, nickel, silver, platinum, etc.), porcelain, fireclay, quartz, Pyrex glass, and other materials (Figures 1, 2). The ability of a crucible made from various clay masses to withstand melting increases to a certain extent with an increase in their porosity. The addition of graphite increases porosity and also gives the crucible a smooth and shiny surface, to which the molten mass does not adhere; furthermore, graphite protects the substance being melted (e.g., steel) from the oxidizing action of oxygen that penetrates the closed crucible during melting.
Figure 1. Porcelain crucible with lid.
Figure 2. Hessian crucible.
Crucibles are produced in various capacities and are usually sold with lids. A platinum crucible easily "burns through" if it is held in the reducing part of a gas flame during calcination; platinum crucibles are unsuitable for work with aqua regia and other liquids that release chlorine or phosphorus, for molten alkalis, or for the calcination of lead, bismuth, or silver oxides, or sulfurous substances. See also Gooch crucible.
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“Crucible.” Soviet Medical Encyclopedia. English translation of Bolshaya Meditsinskaya Entsiklopediya, 1st ed. (Moscow, 1928–1936), ed. N. A. Semashko. https://sovietmedicalencyclopedia.com/article/crucible/