Definition
An evaporating dish is a shallow, heat‑resistant container, typically made of ceramic, porcelain, or silica, designed for the evaporation of liquids in laboratory and industrial settings.
Overview
The primary function of an evaporating dish is to concentrate solutions or to obtain solid residues by heating a liquid until the solvent has vaporized. The open, wide‑mouth design maximizes the surface area of the liquid, promoting rapid evaporation. Evaporating dishes are commonly employed in chemistry, metallurgy, and materials science for tasks such as sample preparation, quantitative analysis of solutes, and the synthesis of small quantities of solid products. They are often used in conjunction with a laboratory hot plate, Bunsen burner, or heating mantle, and may be placed within a fume hood to safely vent vapors.
Etymology/Origin
The term combines “evaporation,” derived from the Latin evaporare (“to turn into vapor”), with “dish,” from Old English disc (“a shallow vessel”). The name therefore directly references the dish’s purpose of facilitating evaporation.
Characteristics
| Feature | Typical Details |
|---|---|
| Material | High‑temperature ceramics (porcelain, alumina, silica), sometimes glazed to improve chemical resistance. |
| Shape | Shallow, usually conical or slightly tapered, with a flat or slightly curved base and a wide opening. |
| Size | Available in a range of diameters, commonly from 5 mm to 150 mm, and depths of 5–30 mm. |
| Heat Resistance | Capable of withstanding temperatures up to 1,200 °C, depending on the material. |
| Chemical Resistance | Generally inert to most acids, bases, and solvents, though highly reactive substances (e.g., HF) may etch certain ceramics. |
| Surface Finish | May be glazed (smooth, non‑porous) or unglazed (porous); glazed dishes are preferred when contamination must be minimized. |
| Usage Considerations | Must be pre‑heated gradually to avoid thermal shock; residues may be removed by mechanical scraping or by dissolving in suitable solvents. |
Related Topics
- Crucible – A deeper, often closed vessel used for melting or high‑temperature reactions.
- Beaker – A cylindrical container with a spout, employed for general liquid handling but less suited for rapid evaporation.
- Drying Oven – An apparatus that removes moisture from solid samples at controlled temperatures, complementing evaporating dishes.
- Distillation – A process that separates components based on volatility; evaporating dishes may be used to pre‑concentrate solutions before distillation.
- Fume Hood – A ventilation device that captures hazardous vapors released during evaporation.
References: Standard laboratory equipment catalogs; Materials science handbooks; Chemical safety guidelines.