Only the diameter is measured in milimetres.
A watch glass hasn't a symbol.
because glass is transparent
Glass bending procedure without dents
Distilled water is used in watch glass cleaning because it is free from impurities that could leave residue or damage the glass. It helps ensure that the watch glass is thoroughly cleaned without leaving streaks or spots behind.
A watchglass can be used as a beaker cover, but you can also place small amounts of chemicals on it and then heat it (for example, to evaporate some water from a wet chemical).From Wikipedia: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. 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.See the Related Questions and Web Links to the left for a picture of watch glass and more information about other laboratory apparatus.
A "crystal" is the transparent cover used to protect a watch's dial and hands. It is mounted in the "bezel" at the front of the case. It is most commonly made from glass, but the more scratch-resistant sapphire is preferred.
i think a test tube
The watch glass may contain small amounts of solid or liquid samples.
It is a millimetre.
A watch with sapphire glass has a transparent cover made from synthetic sapphire crystal. Sapphire glass is highly scratch-resistant, making it more durable and less prone to scratches than other types of watch crystals like mineral glass or acrylic. This results in a clearer and more scratch-free surface for the watch face.
You cannot.
watch glass?