A laboratory container used for experiments, indicating in vitro conditions.A test tube is a small, cylindrical glass or plastic vessel, open at the top and typically rounded at the bottom, used to hold, mix, or heat small quantities of liquids or solids in a laboratory. In physics and chemistry, it is a standard tool for experiments conducted 'in vitro' — that is, outside a living organism, in a controlled artificial environment. The term 'test tube' often appears in discussions of experimental methodology, where it signals that results were obtained under simplified, reproducible conditions rather than in a complex natural setting.
The test tube evolved from early glassware used by alchemists and chemists in the 17th century, but its modern form became standard in the 19th century with the rise of systematic laboratory science. The exact inventor is not recorded.
The test tube's design is simple: its narrow bore minimizes the surface area of the liquid it holds, reducing evaporation and making it easy to observe reactions. Its open top allows for the insertion of pipettes, stirrers, or sensors, while the rounded bottom facilitates even heating when placed in a flame or water bath. In physics, test tubes are often used to hold samples for measurements such as density, viscosity, or optical absorption, where the container's transparency and chemical inertness are key.
Test tubes are ubiquitous in chemistry and biology labs, but in physics they are used for sample preparation in spectroscopy, calorimetry, and fluid dynamics experiments, as well as in educational demonstrations.
The term 'test tube baby' refers to in vitro fertilization, where the conception occurs outside the body, though the actual procedure uses a Petri dish, not a test tube.
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