A watch glass is a fundamental piece of laboratory equipment, typically made of borosilicate or soda-lime glass. It is a shallow, circular disc with a slightly concave surface, resembling the face of a pocket watch. While its name suggests a connection to timekeeping, its primary function lies in scientific experimentation.
Watch glasses have a wide range of applications in the laboratory. They are commonly used to observe chemical reactions, such as color changes, the formation of precipitates, and crystal growth. By placing a small amount of the reaction mixture on the watch glass, scientists can easily monitor the progress of the reaction. Additionally, watch glasses can be used to hold and transfer small amounts of solid chemicals, minimizing the risk of spillage. They can also be used as covers for beakers or flasks, preventing contamination from dust and airborne particles or reducing the rate of evaporation.
Available:
- 60 mm
- 90 mm
- 100 mm
- 120 mm
- 150 mm
- 50 mm
- 70 mm
- 80 mm
- 180 mm
Watch Glass Type:
- Laboratory Equipment (General term).
- Observation Tool (Primarily used for observing and handling small amounts of chemicals).
- Evaporation Dish (Can be used for evaporating small volumes of liquids).
Watch Glass Material:
- Glass (Most common: borosilicate glass, soda-lime glass).
- Plastic (e.g., polystyrene, polypropylene) – Used for certain applications where glass is not suitable.
Usage of Watch Glass:
- Chemical Observations: Observing chemical reactions, crystal growth, and color changes.
- Sample Handling: Evaporating small volumes of liquids, holding and transferring small amounts of solids.
- Covering Containers: Covering beakers or flasks to prevent contamination or evaporation.
How to Use Watch Glass:
- Cleaning: Thoroughly clean watch glasses before and after use to prevent contamination.
- Handling: Handle watch glasses with clean forceps or gloved hands to avoid introducing oils or fingerprints.
- Evaporation: Gently heat the watch glass on a hot plate or water bath for evaporation (if applicable).
- Covering: Place the watch glass over the beaker or flask to prevent contamination or evaporation.