What Is a Watch Glass, and How Are They Used in Chemistry?

Chemists frequently employ round, slightly concave glass objects known as “watch glasses.” In a chemical lab, a watch glass can be used for a variety of tasks, including holding different compounds that a chemist might want to weigh and covering beakers. We’ll examine watch glasses in further detail in this article, including what they are, how they appear, and why chemists need them so much.

A Watch Glass: What Is It?

A watch glass is a piece of glass that is round, as the name suggests. Where does the word “watch” come from? The moniker “watch glasses” comes from the fact that they resemble pocket watch glass in both size and shape. However, a range of glass materials, including borosilicate glass, flint glass, soda-lime glass, etc., can be used to create watch glasses. Other watch glasses aren’t even constructed from glass.

Although they resemble the disposable cups of the chemistry profession and are frequently employed for tasks like fieldwork, plastic watch glasses are also frequently utilised by chemists.

There are many different sizes and thicknesses of watch glasses. What makes the type of watch glass you use important? It probably won’t be a huge deal if you’re just starting out in chemistry and using a watch glass primarily in a classroom setting.

Professional chemists, however, take advantage of the larger selection because some watch glasses better meet their demands for a given experiment than others. For instance, some watch glasses have characteristics like specific ribbing to stop vapours from escaping during an experiment, while others may be made to resist much greater temperatures.

What Function Does a Watch Glass Have in Chemistry?

What precisely is a watch glass used for in chemistry now that you are aware of what it is? In addition to other uses, watch glasses can be used as a platform to hold small objects while they are being weighed. They act as a handy container for powders, liquids, or even corrosive materials in this function.

Consider a scenario in which a chemist needs to add a specific quantity of powder to a recipe. The chemist would lay the powder onto the watch glass and set it to zero weight rather than placing it immediately onto a scale. When they reached the required weight, they may stop adding or removing the powder in question from the top of the watch glass.

Another benefit of a watch glass is that most of them are made with anti-stick features, which prevent substances from sticking to the scale directly. In this method, a chemist won’t have to worry that their weight measurements will be incorrect because of debris adhering to the watch glass itself if they need to utilise a very precise amount of a chemical.

You Can Use Watch Glasses As Beaker Lids

As caps for the tops of the beakers that chemists use for their experiments, watch glasses work great. A chemist can prevent vapours from forming within a beaker from escaping into the air by covering the beaker with a watch glass.

Additionally, watch glasses can help make sure that no unwanted extra ingredients enter and mess up the experiment in addition to keeping vapours inside a beaker.

When liquids are evaporating, watch glasses may occasionally be put on top of beakers containing different liquids. When employed in this manner, the watch glass acts as a plate for collecting particles that evaporate after crystallising on its surface. Chemists are able to observe the entire process in real time because watch glasses are transparent.

Although they are fairly brittle, watch lenses can resist temperatures over boiling. As a result, the scientist doesn’t have to worry about them melting when doing tests.

Utilizing Watches As Drying Tools

Watch glasses are frequently employed by chemists when they need a place for something to dry. When working with a solid substance, a scientist can apply it to the watch glass, which is then placed within a desiccator, a sealable container. After that, the mixture is frequently covered with filter paper and let to dry.

As an alternative, a chemist can hasten the drying process by putting the watch glass containing the chemical within a fume hood. As long as the temperature doesn’t go above a particular level, the watch glass can also be dried by being placed straight into a muffle furnace.

Another option is to position the watch glass inside of a funnel and then blow dry air through the top of the funnel.

Where To Purchase Chemistry Watch Glasses

Do you feel like practising some chemistry? Watch glasses have the advantage of being both easily accessible and moderately priced. There are many different watch glasses available on Amazon that you can have sent straight to your house, even if they might not be the kind of thing you’d find at your neighbourhood Target.

There are numerous additional well-known shops who run sales on their websites. Some of them consist of:

the Scientific Fisher

Chemical Manufacturing Spectrum

Palmer, Cole

You’ll quickly find that there are many different watch glasses accessible in your search. Not sure which option to choose? To assist in limiting your choices, read this assessment of the top lab watch glasses.

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.

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