1. watch glass
Wikipedia definition
2. Watch glassA watch glass is a circular, slightly convex-concave 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.
Read “Watch glass” on English Wikipedia
Read “時計皿” on Japanese Wikipedia
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