Watch glass ? = 45 mm
A clock glass is a kind of laboratory glassware, shaped like a round section of the sphere.
The glass crystal is mainly used in laboratories:
• as a basis for performing simple, drop chemical tests
• as a base for other types of experiments - for example for observing solubility or crystallization
• as a lid for beakers and crystallizers
• as a kind of weighing bottles for weighing small amounts of loose substances.
/ below: photos of three sizes of slides: 45, 60 and 90 mm /