Watch glass

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Caesium fluoride sample on a watch glass
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Caesium fluoride sample on a watch glass

A watch glass is a circular, slightly concave piece of glass used in chemistry as a surface to evaporate a liquid, or as a cover for a beaker. The latter use is generally applied to prevent dust or other particles entering the beaker; the watch glass does not completely seal the beaker, and so gas exchanges still occur.

When used as an evaporation surface, a watch glass allows closer observation of precipitates or crystallisation, and can be placed on a surface of contrasting colour to improve the visibility overall.



Laboratory equipment
Agar plate | Aspirator | Bunsen burner | Calorimeter | Colony counter | Colorimeter | Centrifuge | Fume hood | Magnetic stirrer | Microscope | Microtiter plate | Plate reader | Spectrophotometer | Stir bar | Thermometer | Vortex mixer | Static mixer
Laboratory glassware
Beaker | Boiling tube | Büchner funnel | Burette | Conical measure | Crucible | Cuvette | Laboratory flasks (Erlenmeyer flask, Round-bottom flask, Florence flask, Volumetric flask, Büchner flask, Retort) | Gas syringe | Graduated cylinder | Pipette | Petri dish | Separating funnel | Soxhlet extractor | Test tube | Thistle tube | Watch glass
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