Crucible

Noun

 * 1)  A cup-shaped piece of laboratory equipment used to contain chemical compounds when heating them to very high temperatures.
 * 2) A heat-resistant container in which metals are melted, usually at temperatures above 500°C, commonly made of graphite with clay as a binder.
 * 3) The bottom and hottest part of a blast furnace; the hearth.
 * 4) A very difficult and trying experience, that acts as a refining or hardening process.

Thesaurus
Bunsen burner, Erlenmeyer flask, Kipp generator, acid test, affliction, agitator, alembic, anvil, aspirator, assay, beaker, beater, blank determination, blender, blowpipe, brouillon, burette, caldron, calvary, capillary tube, cement mixer, churn, condenser, criterion, cross, crucial test, deflagrating spoon, desiccator, determination, distiller, docimasy, eggbeater, emulsifier, engine, essay, etna, feeling out, first draft, kiteflying, lathe, machine, matrass, melting pot, mixer, mortar, motor, ordeal, pestle and mortar, pipette, precision balance, probation, proof, reagent bottle, receiver, retort, rough draft, rough sketch, sounding out, standard, still, test, test case, test tube, touchstone, transducer, transformer, trial, tribulation, try, verification, visitation