laboratory glassware; a shallow glass dish used as an evaporating surface or to cover a beaker
crystal, watch crystal, watch glass(noun)
a protective cover that protects the face of a watch
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.
A 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. 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 also sometimes used to cover a glass of whisky, to concentrate the aromas in the glass, and to prevent spills when the whisky is swirled. Watch glasses are so named because they are similar 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.
The numerical value of watch glass in Chaldean Numerology is: 5
The numerical value of watch glass in Pythagorean Numerology is: 5
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"watch glass." Definitions.net. STANDS4 LLC, 2018. Web. 18 Mar. 2018. <https://www.definitions.net/definition/watch glass>.