Erlenmeyer flask (conical flask)
Conical laboratory vessel with a flat base and narrow neck used for mixing, heating, titration, culturing and storage. Common in chemistry and biology labs; made in glass and plastic variants.
Overview
The Erlenmeyer flask, commonly called a conical flask, is a piece of laboratory glassware characterized by a flat, broad base that slopes inward to a narrow cylindrical neck. The geometry permits mixing by swirling with a reduced risk of spillage, and the narrower opening limits evaporation and exposure to the atmosphere. Many flasks carry approximate graduation marks but are not intended as precision volumetric instruments.
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Design and materials
Traditionally Erlenmeyer flasks are made from borosilicate glass because of its resistance to thermal shock and chemical attack. Plastic versions, often made from polypropylene or polymethylpentene, are used where breakage resistance or chemical compatibility at ambient temperatures is required. Flasks come in a range of capacities from small (tens of millilitres) to multi-litre sizes. Some have ground-glass joints, screw caps, or molded side arms to permit connection to tubing.
History and naming
The design is named after the German chemist Richard Erlenmeyer, who described the conical form in the 19th century. Since its introduction it has become a standard vessel in educational and research laboratories for its simplicity and versatility. For the inventor and historical context see Richard Erlenmeyer.
Common uses
Erlenmeyer flasks are used across chemistry and biology for many routine tasks. Typical uses include:
- Mixing and reacting chemicals by swirling to promote homogenization without spilling.
- Heating or boiling solutions on a hotplate or, with appropriate glass, over a flame.
- Carrying out titrations where the narrow neck helps reduce loss of reagent; see resources on titration.
- Growing microbial or cell cultures when fitted with breathable closures or caps.
- Temporary storage of solutions, sampling, and transport inside the laboratory.
- Filtration and vacuum applications using side-armed variants or adapters with Büchner funnels.
Variants and special forms
Several variants exist to match specific laboratory needs. Filter or vacuum flasks have a side arm for connecting to a vacuum source. Heavy-duty flasks are thicker for repeated heating. Wide-mouth versions ease filling and cleaning, while narrow-neck types reduce contamination and evaporation. For general notes on the typical cone-shaped base see cone-shaped base.
Handling, safety and maintenance
Safe use requires attention to temperature changes and pressure. Glass flasks should not be heated while sealed, and rapid thermal shock should be avoided to reduce breakage. Large flasks should be supported with clamps and stands. Cleaning is normally done with detergents and brushes; glass flasks are autoclaved when sterility is required, while some plastics tolerate autoclaving and others do not. Chemical compatibility charts should be consulted before using solvents with plastic flasks.
Accuracy and lab practice
Graduation markings on Erlenmeyer flasks are approximate; when accurate volumes are required, use calibrated volumetric glassware. In titration, for example, flasks are chosen for convenience and mixing rather than metrological accuracy. When used as reaction vessels, stoppers, caps, or adapters can be added to control atmosphere or enable attachments such as condensers.
Educational and practical value
Because of their robustness and multipurpose nature, Erlenmeyer flasks are standard equipment in teaching laboratories and research settings. They offer a good balance between ease of handling, capacity, and the ability to heat or stir samples. For an introduction to laboratory glassware and common vessel types see laboratory glassware and for a basic entry on the item itself see Erlenmeyer flask.
Further reading
For practical guidance consult laboratory manuals and supplier datasheets that describe material specifications, safe operating limits and cleaning procedures. Additional educational resources and methodological notes are widely available for techniques that commonly employ this flask, including titration, culture work and simple distillations.
Applications
- Mixing: By swirling or stirring, liquids can be mixed in the Erlenmeyer flask, suspensions can be kept stable or solution processes can be accelerated. Due to the flat bottom, Erlenmeyer flasks are stable and can be used on magnetic stirrers for mixing substances. The conical shape and narrower neck reduce the risk of splashing compared to open beakers.
- Heating: Erlenmeyer flasks made of glass are suitable for heating liquids.
- Cultivation of microorganisms: Mechanically shaken culture vessels are used for the cultivation of aerobic microorganisms, Erlenmeyer flasks are well suited for this purpose. The Erlenmeyer flask filled with the liquid culture is agitated on a shaking machine to keep the microorganisms evenly distributed in the liquid and to promote gas exchange between the liquid and the gas phase. The size of the Erlenmeyer flasks used varies from millilitre to litre scale depending on the application. Baffles (inward projections) in the Erlenmeyer flask increase turbulence in the liquid during shaking, thereby promoting gas exchange between the liquid and the gas phase. This promotes oxygenation and thus accelerates the growth of the cultivated organisms. This type of cultivation is often used before more technically demanding cultivations are carried out in the laboratory fermenter.
Oxygen supply in shaking cultures
The sufficient supply of oxygen to a liquid culture as well as an optimum pH are basic requirements for all cellular processes. The oxygen concentration in liquid media depends on the amount of oxygen dissolved in the medium, on the amount of oxygen in the gas phase above the culture medium and on the amount of gas bubbles in the medium. The size of the gas bubbles, which are formed by mixing movements, is also of decisive importance for the efficiency of the oxygen input (volume-related mass transfer coefficient, synonym kLa value) into the cultivation vessel. To reduce the formation of foam, anti-foaming agents are sometimes added to stirred bioreactors, which lead to a considerable reduction in the kLa value. Traditional stoppers and the length of the flask neck also reduce the supply of oxygen to the liquid culture. In contrast, Erlenmeyer flasks with baffles increase both the mixing of the liquid and the surface area available for oxygen transfer at the air-liquid interface, leading to a better gas supply to the cells.
Monitoring the oxygen supply and other physicochemical environmental parameters (e.g. pH value, dissolved carbon dioxide concentration) in shake flasks is particularly important in bioprocess technology in order to keep the living conditions in the liquid culture constant. In addition to classical chemical and electrochemical methods for the determination of oxygen concentration, luminescence-based techniques are increasingly used today. The advantage of these optical measurement methods is that no oxygen is consumed in the medium, the measurement is independent of pH and ionic strength and even several metabolic parameters can be determined in parallel under aseptic conditions without taking samples. With this online control, critical process parameter concentrations in liquid cultures can be detected in time and remedied by changing the medium or further processing of the culture.
For good aeration and mixing of the liquid culture, the rotation of the liquid "in phase" is also important, i.e. the synchronous movement with the shaking movement of the tray. Under certain conditions, the shaken culture can get out of phase (out-of-phase phenomenon). This causes the liquid to slosh uncontrollably at the bottom of the flask, resulting in poor mixing, reduced gas-liquid mass transfer and reduced power input. The main factor for a liquid culture getting "out of phase" is the viscosity of the medium. However, small shaking diameters, low filling levels and many and/or large baffles also promote the change of state.
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AlegsaOnline.com Erlenmeyer flask (conical flask) Leandro Alegsa
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