Watch glass

Caesium fluoride

Watch glass

Watch glass and funnel

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Laboratory Watch glasses of different sizes 2

Watch glass is a piece of simple yet essential laboratory equipment used in various scientific fields, including chemistry, biology, and physics. A watch glass is a concave piece of glass that resembles a shallow glass dish or lens. It is primarily used in laboratories for evaporating liquids, holding solids while being weighed, or as a cover for beakers.

Uses

The versatility of a watch glass extends to several key laboratory procedures:

• Evaporation of Liquids: It is commonly used to evaporate liquids to concentrate the solute in a solution. The broad surface area of the watch glass allows for a faster rate of evaporation compared to other laboratory glassware.
• Covering Beakers: A watch glass can be used to cover a beaker to prevent contamination or to minimize the evaporation of volatile substances.
• Holding Solids: When substances need to be weighed, a watch glass serves as a clean platform that does not add significant weight.
• Observation Platform: It can be used as a surface to observe reactions or to hold specimens under a microscope.

Types

Watch glasses come in various sizes, typically ranging from 40 mm to 150 mm in diameter. They are made from different types of glass, depending on the chemical resistance and thermal stability required. Borosilicate glass is a common material due to its resistance to thermal shock and chemical corrosion.

Safety Considerations

While using a watch glass, especially during evaporation or heating processes, it is important to handle it with care to avoid breakage. Sudden changes in temperature can cause the glass to shatter, posing a risk of injury. Therefore, gradual heating and cooling are recommended to ensure safety.

Maintenance

Cleaning a watch glass after use is crucial to maintain its integrity and to prevent cross-contamination between experiments. It should be cleaned with appropriate solvents and stored in a safe place where it is not at risk of being scratched or broken.

Conclusion

A watch glass, though simple in design, plays a crucial role in the laboratory. Its versatility makes it an indispensable tool for scientists and researchers. Proper use and maintenance of a watch glass ensure its longevity and reliability in various scientific applications.

Watch glass Resources
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