1.3. Beakers and laboratory flasks

Beakers (or laboratory beakers) are simple cylindrical vessels with a flat bottom, typically used for the preparation and short-term storage of solutions and liquids (Figure 1.4). Nominal volumes of beakers vary between a few millilitres and several litres. Beakers are usually made of glass or plastics and are graduated, aiding the estimation of the actual volume of the sample. However, precise volumetric measurements are not possible with beakers. Beakers made of heat-shock resistant borosilicate glass are suitable for the heating or boiling of solutions by using a Bunsen burner.

Glass and plastic beakers of different size

Figure 1.4. Glass and plastic beakers of different size.

A variety of flasks are widely used in laboratories, mainly for the storage and preparation of solutions. Some flasks are used with silicone or rubber stoppers, some have standard taper joints equipped with glass stoppers that fit tightly into the opening. Other flasks can be sealed by using a piece of parafilm. Nominal volumes of flasks typically vary between 50 millilitres and several litres. Like beakers, laboratory flasks can be made of glass or plastics. Precise volumetric measurements can only be performed by using volumetric flasks; however, this special subtype is rarely used in biochemical laboratories. The most commonly used flask is the so-called Erlenmeyer flask (also known as conical flask) (Figure 1.5), which has a conical body, a wide and flat bottom and a narrow neck. It is especially suitable for growing bacterial (or eukaryotic) cells in nutrient liquid media inside an incubator at a controlled temperature (Figure 1.5, panel B). Incubators provide continuous shaking of cultures to prevent sedimentation of cells and facilitate gas exchange (oxygen is required for efficient growth), also supported by the shape of the Erlenmeyer flask. (The surface of the liquid is relatively large due to the wide bottom of the Erlenmeyer flask.) The wide and flat bottom also helps in fixing the flasks into the holders of the plate of the incubator, while the narrow neck prevents the culture from spilling out. Openings are covered by a piece of aluminium foil allowing gas exchange while keeping out dust, other bacteria or spores from the environment.

Erlenmeyer flasks for bacterial cell culture

Figure 1.5. A, Erlenmeyer flasks. B, E. coli bacteria growing in Erlenmeyer flasks.