Dropping funnel

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Note the stopcock, glass tube at the left rear, and ground glass joint in this pressure-equalizing dropping funnel.

A dropping funnel is a type of laboratory glassware used to transfer fluids. They are fitted with a stopcock which allows the flow of to be controlled. Dropping funnels are useful for adding reagents slowly, i.e. drop-wise. This may be desirable when the quick addition of the reagent may result in side reactions, or if the reaction is too vigorous.

Pressure-equalizing dropping funnels have a ground glass joint surrounding the stem, allowing the dropping funnel to be fitted directly to the receiver such as a round bottom flask. If the receiver did not have another opening, the flow of fluid will rapidly come to a halt due to the built-up pressure. Thus, a narrow-bore glass tube is connected from the joint to the top of the dropping funnel to allow the overpressure to be relieved.

[edit] See also

• Separatory funnels are similar in shape and design, and may be used as dropping funnels. They do not have the ground glass joint at the stem.