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What is a beaker?

The beaker, also known as a beaker, is a glass material consisting of a straight-walled cylindrical container. Its bottom, unlike flasks and balloons, is flat and has a sharp beak-shaped structure at the top that helps pour the contents of the container.

This glass is constructed primarily of borosilicate. However, in a laboratory there may also be specimens made of stainless steel and aluminum, as well as plastic materials, including polyethylene and propylene.

The invention of the beaker is attributed to Richard Conderbnerellos, although it was John Joseph Griffin who had the greatest contribution to its development. It is usually referred to by the English word “beaker”, a term commonly used in the jargon of teaching and research laboratories.

As can be seen in the image above, one of its main functions is to contain liquids for immediate use. Therefore, it is a container that is always used in laboratories and in any chemical or biological analysis.

Likewise, the beaker is used to heat liquids, prepare solutions, carry out chemical reactions, store substances, collect precipitates, among other uses.

Beaker characteristics

Shapes and walls

The beaker is cylindrical in shape and usually has a height greater than its diameter. Its walls are perpendicular to its base, with the exception of the Phillips-type beaker, which has sloping walls.

Bottom and peak

The beaker has a flat bottom, which facilitates its placement on the surfaces that require it. Likewise, in its upper part it has a spout-shaped structure, which allows the contents of the container to be poured to avoid spillage.

Materials

Glass

The beaker is made mainly of borosilicate glass, a refractory material with high resistance to heating and a low coefficient of thermal expansion. Therefore, your container does not change with heating. In addition, it is resistant to chemical reagents.

However, direct exposure of the beaker to fire should be avoided. To do this, a grid covered with asbestos is used between the fire and the container, which prevents the material from breaking.

Borosilicate glass beakers are produced with volumes ranging from 1 mL to 4 L.

Borosilicate glass used in the construction of beakers is typically from the Pyrex, Kimax, and Corning brand names.

Metals

Beakers can be constructed of aluminum and stainless steel, materials that withstand corrosion. Beakers made of these materials are used primarily for heating liquids, especially in a procedure known as a “water bath.”

Plastics

Beakers are also made of plastic materials, such as polyethylene and propylene, which are capable of withstanding the temperature of 121 ºC used in the autoclave.

Propylene beakers are made with a capacity between 15 and 600 mL. They are very resistant to the action of strong acids, organic solvents and other reagents common in laboratories.

Plastic beakers have many applications, but they do not withstand very high temperatures, so they cannot be used for heating liquids. Some of these materials come with lids and can be used to store substances.

Graduation scale

The beakers finally have a volume graduation scale on their wall , with an indication of 5% error in their reading. The measurement scale does not mean that volume measurements made with beakers have good precision; they only give an approximation of the volume occupied inside.

This graduation scale is sensitive, although not as sensitive as it is with volumetric materials, to sudden changes in temperature. That is why beakers, which withstand high temperatures, must be used for volume measurement. For that you have graduated cylinders, or graduated pipettes.

What is a beaker for?

Beakers are used to perform, among other functions:

  Preparation of solutions of inorganic salts, organic compounds , etc.

–   Preparation of pH buffer solutions.

–   Precipitation of different substances.

–   Carrying out crystallizations of chemical compounds.

–   Storage of substances in those beakers equipped with lids.

 Use to carry out the weighing of hygroscopic substances or with another difficulty to obtain their weight .

 Carrying out the dialysis of solutions packed in tubular containers with semi-permeable membranes.

Types of beakers

The following types of beakers are distinguished: the Griffin, the Berzelius, the crystallization and the Phillips.

Griffin

Griffin-type beaker

The Griffin-type beaker is low-shaped and its height is 1.4 times its diameter. Its walls are straight and its manufacturing volumes range from 20 mL to 4000 mL. These beakers are named in honor of John Joseph Griffin, creator of various laboratory materials.

Berzelius

Note that the Berzelius beaker is much taller than it is wide compared to other models

The Berzelius-type beaker, named after Jöns Jacob Berzelius, is a container that is twice its diameter in height. They are marketed with volumes between 100 and 1000 mL, being used in titrations.

Flat or crystallization

The flat or crystallization beaker has a diameter that is much greater than its height, and is preferably used in substance crystallization processes. It is also used to create hot baths for substances that cannot be directly exposed to fire.

Phillips

Phillips-type beaker. Source: Muskid, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons

The Phillips beaker features sloping walls, showing a conical shape. That is, it has a larger diameter at the bottom than at the top, where it has a beak-shaped structure. This structure differentiates it from the Erlenmeyer flask to which it is similar.

Uses and applications

Weighing of hygroscopic substances

The beaker can be used to weigh highly hygroscopic substances, such as sodium hydroxide (NaOH). The beaker is placed on a suitable balance and its weight is obtained. Then a small volume of water is added, tared, and the sodium hydroxide dragees are added.

Protein precipitation

The beaker can be used in the precipitation of human plasma proteins by chemicals, such as ammonium sulfate. The precipitated proteins are collected from the beaker and dissolved in distilled water.

Then the protein solution is placed on a semi-permeable membrane arranged in a tubular form. The membrane is knotted on one side and the protein solution is placed on it with a Pasteur pipette at the open end, proceeding to close this end.

The protein solution contained in the semi-permeable structure is finally placed in a beaker with water to carry out dialysis, in order to eliminate the ammonium sulfate.

Hot reactions

There are reactions, such as the carbazole reaction for glycosaminoglycans, which require heating through the use of a water bath. The samples are placed in test tubes in a beaker of water, which in turn is heated with a Bunsen burner.

Preparation of buffer solutions

The beaker can be used in the preparation of buffers; for example, that of the phosphate buffer. Monobasic sodium phosphate (NaH 2 PO 4 ) and dibasic sodium phosphate (Na 2 HPO 4 ) solutions are previously prepared . For both solutions the use of the beaker is required.

One of the solutions, depending on the desired pH of the buffer, is placed in a beaker. The electrode of the pH measuring device (pH meter) is inserted into it. And inside the beaker is also placed a magnetic stirrer.

The other phosphate solution is added while the evolution of the pH of the solution is followed in the pH meter. So until the desired pH is reached.

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