crucible, vessel in which a substance is heated to a high temperature, as for fusing or calcining. The necessary properties of a crucible are that it maintain its mechanical strength and rigidity at high temperatures and that it not react in an undesirable way with its contents. Porcelain, iron, and platinum are used in the lab; graphite is usually used in industry, but firebrick is also used, especially when vessels of large capacity are needed. The chamber at the bottom of a metal-refining furnace, where the molten metal collects to be drawn off, is known as a crucible.
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