Watch glass

Watch glass

A watch glass is a circular, slightly piece of glass used in chemistry as a surface to evaporate a liquid, to hold solids while being weighed, 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.

Watch glasses are so named because they are identical to the glass used for the front of old-fashioned pocket watches. In reference to this, large watch glasses are occasionally known as clock glasses.



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  • Watch glass — Watch Watch (w[o^]ch), n. [OE. wacche, AS. w[ae]cce, fr. wacian to wake; akin to D. wacht, waak, G. wacht, wache. [root]134. See {Wake}, v. i. ] [1913 Webster] 1. The act of watching; forbearance of sleep; vigil; wakeful, vigilant, or constantly… …   The Collaborative International Dictionary of English

  • watch glass — noun 1. laboratory glassware; a shallow glass dish used as an evaporating surface or to cover a beaker • Hypernyms: ↑dish 2. a protective cover that protects the face of a watch • Syn: ↑crystal, ↑watch crystal • Hypernyms: ↑prote …   Useful english dictionary

  • watch glass — laikrodžio stiklas statusas T sritis chemija apibrėžtis Įgaubtas disko pavidalo stiklas indams uždengti, reakcijoms atlikti, medžiagoms sverti ir džiovinti. atitikmenys: angl. clock glass; watch glass rus. покровное стекло; часовое стекло …   Chemijos terminų aiškinamasis žodynas

  • watch glass — noun 1》 Brit. a glass disc covering the dial of a watch. 2》 a concave glass disc used in a laboratory to hold material for use in experiments …   English new terms dictionary

  • watch glass — small shallow dish for holding small quantity of a solution; small dish used in laboratories to evaporate liquids (Science); protective transparent cover (glass or plastic) for covering the face of a clock or watch …   English contemporary dictionary

  • watch glass — noun An item of glass laboratory equipment consisting of a simple slightly concave circle of glass. It is a general utility item, used to hold small samples, to evaporate liquids, to cover a beaker, and so on …   Wiktionary

  • watch-glass — hour glass, glass filled with sand that falls to the other side (used to measure time) …   English contemporary dictionary

  • watch-glass — /ˈwɒtʃ glas/ (say woch glahs) noun a transparent cover for the face of a watch …  

  • watch-glass — …   Useful english dictionary

  • Syracuse watch glass — Syr·a·cuse watch glass sir ə .kyüs , .kyüz n a small circular flat bottomed dish of thick glass with a shallow depression used in biology (as for staining, culturing, and various phases of microtechnique) called also Syracuse dish …   Medical dictionary

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