Dropping funnels

A dropping funnel is a laboratory glassware that is used to siphon or add liquids. These laboratory funnels are equipped with a shut-off valve with which the flow can be regulated. Addition funnels are useful for slow, i.e., dropwise addition of reagents. This may be desirable where rapid addition of the reagent may lead to side reactions, or if the reaction is too rapid or violent.

Dropping funnels are usually provided with a ground glass connection at the bottom so that the funnel fits well in, for example, a round bottom flask. This also means that it does not need to be secured separately. However, some models do not have this standard ground joint and must be attached to a plug with a hole.

Pressure compensated dropping funnels have an additional narrow diameter glass tube that connects the top of the funnel to the ground glass joint that surrounds the base. The purpose of this tube is to balance the pressure between the sealed collection bottle and the funnel body. Without it, the fluid flow would quickly stop.