We explain what watch glass used in laboratories is, what it is used for and other characteristics. Also, other laboratory elements.
What is watch glass?
A watch glass or watch glass is known as a laboratory instrument designed as a circular sheet of glass transparent. Its shape is concave-convex and its name comes from its similarity to the glass that covered the face of ancient pocket watches.
It is a common laboratory material, typically used in chemistry. It is often made of a mixture of metal and glass with the purpose of increasing its resistance up to 150 ºC in temperature.
What is watch glass used for?
Watch glass has various uses in the laboratory. The most common is as a container for substances, to weigh or mass them, or to contain potentially corrosive or very hot substances. It is the ideal container for evaporating substances because by resisting above the boiling point of water, it can be heated without fear of melting or destruction.
It can also be used as a lid or cover for a beaker to allow the entry of air and gas exchange, while preventing the entry of dust into a substance that is needed pure and uncontaminated.
Watch Glass Features
The watch glass is always round, medium in size and delicate in nature, that is, fragile to mechanical impacts despite its resistance to corrosive chemical agents or relatively high temperatures. It is transparent, lightweight and more or less cheap to manufacture.
Other laboratory instruments
Other common materials or instruments in the laboratory are the following:
- Petri capsule Also known as a “plate” or “box”, it is a round, transparent container with a cover of the same material, made of plastic or glass, and capable of being closed, although not hermetically. It is used for cell culture and to contain biological specimens whose behavior is to be observed.
- Test tube. It is a glass tube (although there are also some made with certain plastics today) with a cylindrical shape. It is open at one end, and at the other it is closed with a hemispherical shape. It is used to contain medium or small samples (liquid or solid), and also to generate small chemical reactions inside.
- Agitator It is a glass rod (although it could be made of another material) that is used to stir or stir mixtures. Nowadays, mechanical agitators have been developed that use another way to stir the mixtures.
- Pipette It is an elongated, cylindrical instrument used to measure volumes of liquids. It can be made of glass or plastic and of different designs.
- Test tube It consists of a graduated glass (sometimes plastic) container used to measure volumes of liquids. It has a cylindrical and elongated shape, and rests on a base.
- Burette. It is a graduated container used to measure volumes of liquids. It has a cylindrical and elongated shape. It can be made of glass, and nowadays, rubber burettes are also manufactured. The upper end is open and the lower end contains a key that, when opened, lets out the liquid whose volume is to be measured.
- Beaker This is a thin cylindrical container, with a flat bottom and printed capacities along its height, ranging from a few milliliters to several liters in capacity. It can be made of metal, borosilicate glass or plastic.
- Settlement ampoule Also called a separatory funnel, it is a glass container with a plastic lid on top and a closing tap at the bottom, which culminates in a tube. It serves precisely to decant substances. It is shaped like a transparent cone.
- Erlenmeyer flask It is a glass bottle with a body wider than its upper cylindrical mouth, whose shape is useful for making mixtures by stirring, or to allow the controlled evaporation of fluids. It is usually labeled on its side.
- Distillation flask Also called “distillation flask” or “Florentine flask”, it is a flask with a long neck and spherical body, designed to allow the uniform heating of substances and the redirection of vapors. In its neck it generally has a lateral release tube through which gases or vapors can be redirected.
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References
- “Watch glass (chemistry)” on Wikipedia.
- “Clock glass” at TP Chemical Laboratory.
- “Clock glass” in the Science Laboratory of the National University of the Center of the Province of Buenos Aires (UNICEN).
- “Watch glasses” at VWR part of avantor.
- “Chemistry Laboratory Glassware Gallery” at ThoughtCo.
