Beakers and graduated cylinders are bare essentials that every laboratory, classroom and research facility needs to have on hand. But while they serve a similar purpose, they are not always interchangeable for applications that require precision and accuracy. Take a closer look at how these tools should be used in the lab so you can always obtain the best possible results.
Beakers are stout, flat-bottomed containers that are generally 1.5-2 times as tall as their base diameter is wide. They usually have a spout on one side to make pouring liquids easier and are most often used for performing simple reactions, titration or mixing, heating and holding fluids.
Similar to cylinders, beakers are graduated with volume measurements. In that case, why is a graduated cylinder more accurate than a beaker? The volume marks on a beaker are only approximate values, and therefore only provide whole numbers. For example, a 100 mL beaker might only have marks for every 20 mL, so it would be tricky to gauge the exact volume of a liquid sample falling between the 60 mL and 80 mL marks. If the test you're performing requires precision, a beaker is not the tool you should use.
There are three main types of beakers that every lab should have on hand:
- Glass Beakers: These classic beakers have reinforced rims, uniform wall thicknesses and optimal clarity for sample observation.
- Plastic Beakers: Generally made of polypropylene or polymethylpentene for their chemical resistance and excellent clarity, respectively. These beakers also tend to be lighter and less fragile than glass.
- Stainless Steel Beakers: Great for heavy-duty applications. While they aren't transparent, they are smooth, seamless and corrosion resistant, so they're great for collecting and heating corrosive solvents and extracts.
Graduated cylinders are tall, narrow cylinders with flat bases. Some cylinders will have spouts, like beakers, but it's also common for them to have flat, uniform rims. Graduated cylinders have markings every 1 mL, making it easy to get a fairly precise volume measurement from your liquid sample. For the best results, you should observe the surface of the liquid inside a graduated cylinder at eye level; the line at the bottom of the liquid's meniscus indicates the sample's volume.
Graduated cylinders are designed to determine the volume of a sample by noting the difference in liquid volume before and after the sample is added to the cylinder. Although their measurements are made for accuracy, more advanced volumetric analysis should be performed with volumetric flasks or pipettes.
Additionally, graduated cylinders come in two classes of accuracy, as designated by ASTM: Class A and Class B. Class A graduated cylinders have double the accuracy of Class B and are also made of sturdier materials, like borosilicate glass, that are ideal for long-term exposure to chemicals. These cylinders can have either single or double measurement scales.
It's important to have both glass and plastic graduated cylinders on hand in your lab: