An apt rubber stopper definition would be a small, usually conoid or tapered plug used to conceal the openings of test tubes, vessels, flasks, and many other containers, especially glassware. Stopper plugs made of cork are available, too. But, rubber stoppers are generally preferred to stoppers made of different materials. They provide a better temperature and chemical resistance.
As the rubber stopper definition suggests, a rubber stopper’s chief function is to disguise and conceal holes. It is used in laboratories worldwide to block a gas or fluid from escaping its vessel while performing a scientific experiment. Another primary function of rubber stoppers is to limit chemical samples’ corruption by oxidation, as it protects them from being exposed to air. Finally, rubber stoppers also enable efficient shaking or mixing of chemical solutions without causing spillage.
Rubber stoppers may also be used to seal off the mouth of a test tube.
The most common shape of rubber stoppers is cylindrical, having a tapered or conoid bottom surface. Many commercially available rubber stoppers have one or two holes in them that allow the insertion of test equipment such as a thermometer, thermostat, pipette, etc. The size of a rubber stopper, as described by the rubber stopper definition, is small. Conventionally, its height ranges from 0.5 inches in diameter to 5 inches in width at its top. The conoid bottom surface ranges from 5/16 inches to a maximum of 3.5 inches. Stoppers smaller in size are best for test tubes and other glassware, whereas stoppers that are big are better for flasks, vessels, and beakers. The central properties of stoppers, highlighted by the rubber stopper definition, are their impermeability, chemical and temperature resistance, and elasticity. These attributes make rubber stoppers safe to use and remarkably efficient at concealing the openings.