Volumetric flask: description, purpose, features of use. Volumetric flask - an indispensable laboratory tool

The main laboratory chemical glassware includes flasks, glasses, test tubes, cups, funnels, refrigerators, reflux condensers and other vessels of various designs. Most often, chemical glassware is made from glass of various grades. Such dishes are resistant to most chemicals, transparent, easy to clean.

Flasks, depending on their purpose, are made in various capacities and shapes.

a - round bottom; b - flat-bottomed; in - round-bottomed with two and three necks at an angle; g - conical (Erlenmeyer flask); d - Kjeldahl flask; e - pear-shaped; g - sharp-bottomed; h - round-bottom for distillation (Wurtz flask); and - sharp-bottomed for distillation (Claisen flask); to - Favorsky's flask; l - flask with a tube (Bunsen flask)

a - a glass; b - buks

Round bottom flasks are designed for high temperature, atmospheric distillation and vacuum applications. The use of round-bottom flasks with two or more necks makes it possible to simultaneously perform several operations during the synthesis: use a stirrer, refrigerator, thermometer, dropping funnel, etc.

Flat-bottom flasks are suitable only for operation at atmospheric pressure and for the storage of liquid substances. Conical flasks are widely used for crystallization because their shape provides a minimum evaporation surface.

Thick-walled conical flasks with a tube (Bunsen flasks) are used for vacuum filtration up to 1.33 kPa (10 mmHg) as filtrate receivers.

The beakers are intended for filtration, evaporation (at a temperature not exceeding 100 °C) and preparation of solutions in laboratory conditions, as well as for carrying out separate syntheses in which dense, hard-to-remove precipitates are formed from the flasks. Do not use beakers when working with low-boiling or flammable solvents.

Bottles, or glasses for weighing, are used for weighing and storing volatile, hygroscopic and easily oxidized substances in air.

Cups are used in evaporation, crystallization, sublimation, drying and other operations.

Test tubes are available in various sizes. Test tubes with a conical section and a drain tube are used for filtering small volumes of liquids under vacuum.

Glass laboratory equipment includes. also connecting elements (transitions, allonges, nozzles, closures), funnels (laboratory, separating,

a - cylindrical with a developed edge; b - cylindrical without limb; c- sharp-bottomed (centrifuge); g - with interchangeable conical sections; d - with a conical section and a drain tube

The connecting elements are intended for assembly on thin sections of various laboratory installations.

Funnels in a chemical laboratory are used for pouring, filtering, and separating liquids.

Laboratory funnels are used for pouring liquids into narrow-necked vessels and for filtering solutions through a paper pleated filter.

a - laboratory; b - filtering with a soldered glass filter; into dividing; g - drip with a side tube for pressure equalization.

Funnels with glass filters are usually used to filter aggressive liquids that destroy paper filters.

Dividing funnels are designed to separate immiscible liquids during extraction and purification of substances.

Drip funnels are designed for controlled addition (adding) of liquid reagents during the synthesis. They are similar to separating funnels, but their different purpose predetermines some design features. Drip funnels usually have a longer outlet tube and a tap located under the tank itself. Their maximum capacity does not exceed 0.5 liters.

Desiccators are used for drying substances under vacuum and for storing hygroscopic substances.

Cups or glasses with substances to be dried are placed in the cells of porcelain inserts, and a substance is placed on the bottom of the desiccator - a moisture absorber.

a - vacuum desiccator; b - normal

Refrigerators laboratory glass apply to cooling and condensation of vapors.

Air coolers are used for boiling and distillation of high-boiling (ґklp > 160 °С) liquids. The cooling agent is the ambient air.

Water-cooled refrigerators differ from air-cooled refrigerators by the presence of a water jacket (the cooling agent is water). Water cooling is used to thicken vapors and distill substances with< 160 °С, причем в интервале 120-160 °С охлаждающим агентом служит непроточная, а ниже 120 °С - проточная вода.

The Liebig refrigerator is used to distill liquids.

Ball and spiral coolers are most applicable as return liquids for boiling liquids, as they have a large cooling surface.

Dephlegmators serve for more thorough separation of the fractions of the mixture during its fractional (fractional) distillation.

In laboratory practice, for work related to heating, porcelain dishes are used: glasses, evaporating cups, crucibles, boats, etc.

a - evaporating cup; b - Buechner funnel; c - crucible; g - mortar and pestle; d - spoon; e - glass; g - a boat for burning; h - spatula

For filtering and washing precipitates under vacuum, porcelain suction filters - Buchner funnels are used.

Mortars with pestles are designed for grinding and mixing solid and viscous substances.

To assemble and fix various devices in a chemical laboratory, tripods with sets of rings, holders (legs) and clamps are used.

To fix the test tubes, racks made of stainless steel, aluminum alloys or plastics, as well as manual holders, are used.

a - tripod; b - manual holders

The tightness of the connection of the components of laboratory instruments is achieved with the help of thin sections, as well as rubber or plastic plugs. Stoppers are selected by numbers that are equal to the inner diameter of the closed neck of the vessel or the opening of the tube.

The most universal and reliable way of sealing a laboratory instrument is to connect its individual parts with the help of conical sections by joining the outer surface of the core with the inner surface of the coupling.

Volumetric flasks - traditional for various measurements, experiments, research. They were invented several centuries ago, but to this day they have not lost their relevance.

Design features, manufacturing principles

Volumetric flasks are presented in the form of glass or plastic vessels of a conical shape (flasks with a pear-shaped or spherical base, a long cylindrical neck and a flat bottom are also available). Glass flasks are made from light or dark glass raw materials with low expansion rates. The capacity of vessels of this type can vary from 1 ml to 5 liters.

The manufacture of the neck of the volumetric flask is carried out with a section for a ground glass stopper, or without a section. If the product is without a thin section, then it is closed with a cotton, polyethylene, silicone, rubber stopper (if the specialist works with strong-smelling or volatile substances). Flasks with a thin section are designed for long-term storage of solutions and substances in them.

Volumetric flasks have a flat bottom because the vessel must be as stable as possible on a horizontal surface or on a slightly inclined surface. An empty 25 ml flask should no longer roll off a surface with an inclination of 15 degrees or less. Small vessels should remain stable when tilted at 10 degrees.

Volume marks are usually applied to the neck.

• If the product has one label, then it is intended "for infusion".
• If the product has two labels, then it is used "for pouring".
• There are also volumetric flasks with a scale on the neck, with an extended upper part of the neck for a funnel and other types of vessels.

The production of volumetric flasks is carried out in accordance with the requirements of GOST and international standards. In the factory, each vessel is calibrated according to the required accuracy class, for which GOST defines the maximum error limits at a temperature of 20 degrees.

What are measuring flasks for?

Products of this type are used to prepare chemical solutions of a certain concentration directly in the vessel. Graduation occurs due to the circular mark on the flask, which indicates the nominal volume of the liquid in the vessel. When pouring the solution from the flask, it is necessary to take into account the remains of the liquid that linger on the walls of the vessel. That is why, as a result, the volume of the poured solution will become less than it was in the flask.

Volumetric flasks that work "for infusion" and "for pouring" have two marks: the lower mark is used if only the volume of the infused liquid needs to be measured; if measurement of the poured liquid is required, the upper mark is used.

Flasks with a measuring scale on the neck are used to work with solutions made from two constituent liquids. The presence of graduation allows you to determine the decrease or increase in volume when one substance is dissolved in another.

How to work with volumetric flasks?

All volumetric flasks are marked: there is information about the accuracy class of the vessel, the nominal volume, the manufacturer, the calibration temperature, the type of glass used, etc.

When conducting laboratory tests, products must not be heated (even during thermal sterilization). To increase the measurement accuracy, it is recommended to set the temperature in the room to the same temperature as when the vessel was calibrated by the manufacturer. For this, a specialized laboratory is used.

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A flask is a vessel with a wide base and a long cylindrical neck. However, over the centuries, many types of flasks have been developed for different tasks, which determined the shape of a particular vessel. Now in the arsenal of chemists there are flasks with a spherical, pear-shaped and conical base, with high and low, wide and narrow necks.

Distinctive features of a flat-bottomed flask

As the name implies, flat-bottom flasks are flasks with a flat bottom. Their main advantage is that the researcher does not need to worry about how to set up the vessel, because a flat-bottomed flask does not need a tripod or a special stand. It is tabletop stable, lab tile stable, easy to store and use in lab setups.

Classification of flat-bottomed flasks:

All flat-bottomed flasks can be classified according to different criteria:

By capacity: the capacity of the flasks varies from 5 ml to 50 l.

Heat resistant and non heat resistant.

According to the method of application:
reaction flasks;
measured;
receiver vessels.

By form:
round flasks;
conical flasks.

Flat bottom flasks, like round bottom flasks, can have multiple necks. But such vessels are rarely encountered and used and are usually made by special order.

Each type of flask has its own advantages. For example, quartz flasks are distinguished by increased heat resistance, and glass flasks, although they cannot compete with quartz flasks in this indicator, are usually cheaper and more practical for standard tasks. Round flat-bottomed flasks are more convenient as reaction vessels, while conical flasks are more suitable as receiver vessels. Volumetric flasks, as a rule, are round, small in volume, with a long narrow neck, which makes it possible to mark the amount of a substance with high accuracy.

Flasks with polished necks are very convenient. They can store prepared solutions and substances obtained as a result of synthesis. A conical flask with a thin section is good because you can insert an adapter or another device into it, say, a refrigerator, so that the connection is both hermetic and easily disassembled (assembled).

Personalized flat-bottomed flasks

The most famous flat-bottomed flasks are the Bunsen flask. and an Erlenmeyer flask. The Erlenmeyer flask is conical, with a wide base and a low neck. Several divisions of the approximate volume scale are applied to its walls, as well as a white matte rectangle for pencil marks. The flask is very stable, suitable for the use of mechanical and magnetic stirrers. The wide base and narrow neck make the vessel extremely practical - liquids do not spill during transportation and mixing. The wide bottom is convenient for laboratory tiles. Erlenmeyer flasks are used for analytical work, titration, gas production, as a reaction or receiving vessel, washing.

The Bunsen flask is also conical, designed for vacuum filtration. It is made of thick glass, on the side, in the upper part it is supplied with a side outlet for connecting to a vacuum pump or vacuum line. A funnel is inserted into the neck through a rubber stopper.

Need to buy flasks for chemistry?

In the Prime Chemicals Group store, you can buy chemical flasks of various shapes, sizes and purposes: glass laboratory flasks, flasks for chemical experiments, for production, for medicine and other industries. Prices and level of service will pleasantly surprise you.

Laboratory glassware is distinguished by its diversity. It is used in the process of conducting analyzes in various fields. A huge number of variations of the containers presented allows you to use the most suitable variety in each case.

Existing types of flasks can be classified according to some criteria. This allows you to delve deeper into their application and significance for analysis. Varieties of laboratory glassware deserve special attention.

general characteristics

Most commonly used in laboratory studies glass flasks. They allow you to perform many different operations and chemical reactions. A rather large expense item for any laboratory is precisely the container.

Since most flasks are made of glass, they can break. Today there are many different types of flasks. They may be exposed to temperatures or chemicals. Therefore, the material from which laboratory glassware is made must withstand such loads.

Flask configuration can be very unusual. This is necessary in order to conduct a full as well as analysis of the required substances. Most often, these containers have a wide base and a narrow neck. Some of them may be equipped with a cork.

Varieties of form

In laboratory studies, flat-bottomed and round bottom flask. These are the most commonly used types of containers. Flat-bottomed varieties can be placed on a flat surface. Their purpose is very varied.

The round-bottom flasks are held in a rack. This is very convenient if the container needs to be heated. For some reactions, this speeds up the process. Therefore, the round-bottom flask is most often made from heat-resistant glass due to this application feature.

Also, both presented varieties of laboratory glassware are used to store various substances. Sometimes, in very rare cases, sharp-bottomed varieties of containers are used in the course of laboratory analysis.

The use of flasks and their configuration

Very varied. They depend on the application. The Kjeldahl flask is pear-shaped. It is most often used in the device of the same name for the determination of nitrogen. This flask may have a glass stopper.

A Wurtz flask is used to distill various substances. In its design there is a discharge tube.

The Claisen flask has two necks, the diameter of which is the same along the entire length. A tube is connected to one of them, designed to remove steam. The other end communicates the dishes with the refrigerator. This variety is used for distillation and distillation at normal pressure.

The Bunsen flask is used in filtration processes. Its walls are very strong and thick. At the top there is a special process. It approaches the vacuum line. For experiments under reduced pressure conditions, this variety is ideal.

Erlenmeyer flask

Considering the existing types of flasks, it is impossible not to pay attention to another form of laboratory glassware. The name of this container is given in honor of its creator - the German chemist Erlenmeyer. This is a conical container that has a flat bottom. Its neck is characterized by a cylindrical shape.

This flask has divisions that allow you to determine the volume of liquid inside. A unique feature of this type of container is an insert made of special glass. This is a kind of notebook. On it, the chemist can make the necessary notes.

The neck, if necessary, can be closed with a stopper. The conical shape promotes high-quality hashing of contents. The narrow neck prevents spillage. The evaporation process in such a container is slower.

The flask of the presented type is used when carrying out titration, cultivation of pure cultures or heating. If the flask has divisions on the body, they are not heated. Such dishes allow you to measure the amount of the content of the substance.

A few more features

The types of flasks used can also be divided into groups depending on the type of neck. They are simple (for a rubber stopper), as well as with a cylindrical or conical section.

Depending on the type of material from which the cookware is made, it can be heat-resistant or plain. By purpose, the flasks can be divided into volumetric containers, receivers and reactors.

The volume of laboratory glassware is also quite diverse. Their capacity can be from 100 ml to 10 liters. There are flasks of even larger volume. When working with such containers, it is imperative to follow safety rules. Each type of equipment presented must be used strictly for its intended purpose. Otherwise, you can break the flask or harm your body.