In small-scale experimental setups involving noncorrosive gases, bungs constructed of vulcanized rubber are often utilized in chemistry.
Some chemical plugs include one or more holes that allow a glass tube or laboratory funnel to be placed through the plug and into a container or other piece of equipment.
The rubber bung may be used to seal a flask because the user may need to mix the contents by shaking the flask or may need to keep the contents inside the flask and prevent leakage.
In all circumstances, the bung maintains the experiment’s environment’s seal, preventing liquids or gases from escaping (or enter).
Standardized glass stoppers and connectors are favored for applications that set higher demands on the bung in terms of temperature and mechanical durability or solvent resistance.