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An evaporating dish or evaporating basin (sometimes referred to as watch glass) is a laboratory item used for the evaporation of solutions and supernatant liquids, and sometimes to their melting point.
Evaporating dishes are used to evaporate excess solvents, most commonly water, to produce a concentrated solution or a solid precipitate of the dissolved substance.
Evaporating dishes have the appearance of a thin concave dish with a beak, though some models may have flat bottom. The most common type is made of glazed fired porcelain, though all-glass versions exist. Plastic evaporating dishes are rarely encountered or used, as repeated heating will deform or wear them.
Evaporating dishes can be bought from lab suppliers or online.
Alternatively, you can use glazed porcelain dishes, though you may not reuse them for food after being exposed to lab reagents or contaminated suspensions/solutions. Glass dishes or cups may also be used.
- Evaporate solutions
- Recrystallize compounds
The glazing covering the inside of the dish resists the attack of many acids, but will be attacked by alkali at high temperatures.