testtube

A test tube is a small cylindrical laboratory glassware vessel used to hold, mix, or heat small quantities of liquid or solid reagents. It is open at the top and closed at the bottom, typically ranging in capacity from a few milliliters up to about 50 milliliters.

Most test tubes are made of borosilicate glass for chemical resistance and thermal stability, though plastic variants such as polypropylene are used for disposable or non-reactive samples. Glass tubes may be clear or color-coded at the rim for identification and sometimes marked with graduations.

Standard sizes include approximately 75 to 100 millimeters in length and 10 to 20 millimeters in diameter. Specific forms include smaller microtubes and larger boiling tubes, which have thicker walls and wider mouths for heating.

Common uses include conducting qualitative or quantitative reactions, heating or cooling small samples, mixing reagents, and holding specimens in chemistry, biology, and environmental testing. In microbiology, culture tubes resemble test tubes but may have different bottoms or caps designed for growing microorganisms in liquid media.

Handling and safety: glass test tubes can break or crack under stress, so care is required. When heating, tubes should be held with tongs and heated gradually; never sealed while hot. Use racks, clamps, and appropriate labeling, and wear eye protection.

Cleaning and disposal: glass tubes are typically cleaned by rinsing and may be autoclaved for sterilization or cleaned with detergents. Plastic tubes are often intended for single use and disposed of according to local regulations for chemical or biological waste.