Other Definitions
watch glass (dict)
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Watch GlassIn a chemistry laboratory a watch glass is a small concave circular piece of glass. It is used either as surface to evaporate a liquid or as a cover for a beaker (non-sealing, it will slow but not stop evaporation and will prevent dust from falling into the beaker but not stop gas exchanges). When used as an evaporation surface it can be used to closely observe precipitates or crystallization; placing on a surface of contrasting color will improve visibility.
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