- Dropping funnel
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Note the stopcock, glass tube at the right, and ground glass joint in this pressure-equalizing dropping funnel. An ordinary dropping funnel lacks the pressure-equalizing glass tube at the right side.
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.
Dropping funnels are usually fitted with a ground glass joint which allows the funnel to fit snugly onto, e.g. a round bottom flask. This also means it need not be clamped separately.
Pressure-equalizing dropping funnels have an additional narrow-bore glass tube from the bulb of the funnel, to the ground glass joint around the stem. Without means to equalize the pressure between a sealed receiving flask and the bulb of the funnel, the flow of fluid will rapidly come to a halt.
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.
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