CRUCIBLE (ML. en/cam/um, crusibulu in, melting-pot, from OF. cruchc, Port. erugo, crock, from 011t,I. eh rimy, Ger. Krug. AS. crop, jar, Ir. (-royal,. Gael. crag, Welsh crochan, pitcher; confused by popular etymology with Lat. crux. cross). A vessel for heating and fusing metals. glass. and other materials requiring a great. de gree of heat for their melting. Crucibles are made in all sizes, from that of a lady's thimble to one which will hold 400 pounds of molten zinc. The essentials in their construction are that they be made to endure extreme heat with out fusing, and sudden changes of temperature without breaking. A great variety of materials are used for making crucibles, as clay. plumbaro, graphite, lime. aluminum. and platinum. crucibles are more nr less acted on by litharge, hut a chalk lining makes them less so. The most common form is the Tressign crucible, made of equal parts of tire-clay and coarse sand. It will stand extreme beat, hut not very sudden changes in temperature. This is the cheapest variety.
and is adequate for all ordinary processes of ex perimenting and refining. They come in nests. in sizes varying from two to eight inches in di ameter. Cornish crucibles are clay crucibles of a coarse grain and mottled grayish-white color. They endure sudden changes of temperature. but cannot be heated to whiteness. They are much used for copper-assaying. Plumbago or coke crucibles are of great value in the fusion of cer tain metals. Graphite crucibles meet all tem perature conditions, but are slowly acted on by metallic oxides or gases. Lime crucibles are absolutely infusible. .11a ni in um crucibles 1)(3 suss the advantage of not being readily acted on by the materials fused, even sodium having no effect on them. They are also little affected by changes of temperature. The celebrated Berlin, crucibles are made of a composition of several non-fusing materials, which contains S parts of fire-clay, 4 parts of black lead, 5 parts of pow dered coke, and 3 parts of old crucibles.