Basic tools of the chemistry lab


This page describes some basic pieces of glassware that are commonly used in a chemical laboratory. Choosing the right tool for the job will make things go much easier while you experiment. It's worth learning about these before you do too much work in the lab.

Here we'll cover these common pieces of lab equipment:


Beaker


The Pyrex™ beaker is a staple of laboratory glassware. If you have nothing else, you've got to have a few beakers around.

Beakers are good for holding and mixing solutions, collecting samples, performing reactions – a whole host of uses.

A beaker is not a piece of precision glassware. Notice that on the one illustrated here, the graduations are given with a tolerance of ±5%. That means that if you fill the beaker up to the 60 ml mark, you're only guaranteed to have between 57 (60 ml - 5%) and 63 (60 ml + 5%) milliliters of liquid. That's fine for some applications, but terrible for others. You'll need to know your experiment and the errors in volume measurement that it will tolerate before trusting the volume markings on a standard beaker.

Beakers come in standard height and tall-form, and in sizes from 25 ml or so to more than 2 liters. They also come in standard and heavy-duty Pyrex™ glass.

Pro tip: Don't fill a beaker to its highest marking, especially if you need to swirl or stir the solution, or if it might bubble or foam. Use a bigger beaker to avoid sloshing its contents.


Erlenmeyer flask


Think of an Erlenmeyer flask as a special kind of beaker. It's probably the second most-used piece of lab glassware. It's used for all the reasons a beaker is, but has the advantage of a long, narrow neck. The extended neck makes it possible to swirl a solution vigorously without spilling, and it makes the vessel fairly easy to pour.

The neck design also holds in heat and can be used to channel and collect any gas evolved in a reaction. It can be fitted with a stopper (e.g. with a hole in it for a piece of tubing) for that purpose, or a ball of cotton for applications in which the contents need to be kept sterile.

Like a beaker, an Erlenmeyer flask is not a piece of precision glassware. The printed graduations on the side (if any) are good only to about ±10% of the volume. Erlenmeyer flasks are seldom used to measure liquid volume.

Pro tip: If you've filled an Erlenmeyer to the point where the liquid level is in the neck, you need a bigger Erlenmeyer.

The Erlenmeyer flask is named for its inventor, German chemist Emil Erlenmeyer (1825-1909). German scientists were crucial to the early development of chemistry.


Round-bottom flask


The round-bottom flask is a specialty item of lab glassware that isn't used much, but when it's needed, it's awfully handy. It's especially good for running reactions that require constant heating or boiling. It's shape fits snugly into electric heating mantles, the temperature of which can be controlled more precisely than a burner or hot-plate top.

Round-bottom flasks are often fitted with glass joints that can be sealed, so that a reaction can be isolated from the outside atmosphere (for example, if you wanted to run a reaction without the presence of oxygen) or so that any evolved gas can be collected. The near-spherical shape also makes the round-bottom flask strong when subjected to an internal vacuum – it's less likely to implode.

Round-bottom flasks come in sizes from a few milliliters to a liter or more, and they typically have no volume markings.

Pro tip: If you're using a round-bottom flask on a bench-top, be sure to have a cork ring to set it on, lest it roll away. In a pinch, an empty beaker will due to balance one in between tasks.


Test tubes


What lab would be a lab without test tubes? The main advantage of a test tube is to be able to perform a reaction or an observation using very small volumes.

Test tubes, usually glass, but sometimes plastic, come in a wide array of depths and diameters. You should be able to find one for your particular use.

If you use a lot of test tubes, you'll need a rack to store them upright, though an empty beaker will hold a few vertically-enough in a pinch. If your tube will get hot or if you're concerned about overflow or splashing, a test-tube holder – wire or plastic – will come in handy.

Test tubes can take a stopper, and some have screw caps. The variety is endless.

Test tubes allow us to shrink the size of some of the chemistry we do, so that our chemical waste stream isn't so great. That trend, in recent years, has been taken to extremes with the development of 96-well plastic plates – really a grid-shaped pattern of 96 very small test tubes. Those have given way to 384-well plates, and so on. A great deal of chemistry is now even done in microscopic bits on the surface of microchips. All of this has led to the ability to do more chemistry faster and with far less waste.


Microchemistry

A good deal of chemistry is now performed on plastic plates like these, that contain wells designed to hold 20 microliters of liquid or less, and typically come in 96- and 384-well versions. They allow a chemist to run a great many reactions at once, and for robotic loading and measurement of the outcome of a reaction. They have vastly reduced the amount of chemical waste generated in labs while increasing the number of experiments that can be run at once.




Graduated cylinder


The graduated cylinder is the most basic piece of volumetric glassware in the lab. The word volumetric (volume measure) is used to describe lab ware that can be used to measure liquid volumes more precisely than a beaker or flask.

The example illustrated here is a 100 ml cylinder marked in 1 ml increments. Often the markings are placed (etched or printed) on volumetric glassware after they have been formed by blowing or molding. This ensures that small differences in shape don't lead to volume inconsistencies from cylinder to cylinder.

The inset shows that a liquid, particularly an aqueous (water-based) liquid, tends to climb the walls of the cylinder a bit, forming a U-shaped meniscus. We read the volume level of a graduated cylinder at the bottom of the meniscus.

In this example, the volume is about 73.8 ml. Notice that I've estimated that the level is about 80% of the way to the 74 ml line. That estimate causes some uncertainty, perhaps ±0.5 ml, but that's only about 0.07% of the total volume, much better than measuring volume with a beaker.

The wraparound ring on this cylinder (covering the 90 ml mark) can be found on many glass cylinders. It is there to keep the cylinder from breaking should it fall over and it's a good idea to use it.

Some people use it to help read the level of the meniscus, but you should get used to doing that without the ring. Make sure to keep your eye (and safety glasses!) level with the meniscus for an accurate reading.

Graduated cylinders come in sizes from about 10 ml to 2 liters or more.


Pipets


The pipet (sometimes spelled pipette) is the gold standard for quantitative measurement of liquid volumes. If you need as close to a milliliter (ml) as you can measure, use a 1 ml volumetric pipet.

Pipets come in a wide variety of sizes, shapes and designs. The one illustrated on the left is designed to measure and deliver only 1 ml of liquid. To use it, one fits a suction device (there are many kinds) to the upper end, sucks up liquid so that the bottom of the meniscus is aligned with the line – usually etched into the glass – and then the liquid is allowed to run out under the force of gravity. The 25 ml pipet on the right works on the same principle, except that it has an enlarged portion (bulb) that gives it a higher capacity.

TD / TC

Some pipets have a designation, usually found right under the volume label at the top, that says TC or TD. TC means "to contain," and TD means "to deliver." Most volumetric pipets are TD devices. This means that when they are emptied, one does NOT blow out the small amount of liquid that remains in the narrow outlet of the pipet, though it is acceptable to touch the pipet to the inside of the beaker or flask to remove a last hanging drop. It's meant to be retained, and the delivered volume will be accurate.

TC pipets are generally blown out either by a bulb or other reversible suction device, so that they contain no more liquid. Larger, and less precise pipets are usually TC devices.

Pro tip: One drop of liquid that falls from a typical pipet is about 1/20 (0.05) of 1 ml. A drop falls because as it grows, the internal cohesion between water molecules becomes less than the downward pull of gravity. This occurs at about the same drop size in all water drops.


Buret


A Buret is a specialized kind of pipet fitted with a valve or stopcock that allows us to release controlled amounts of liquid that can be measured by noting the starting and ending volumes. Burets are used for procedures known as titrations.




Crucible


A crucible is a porcelain container used for heating mainly solid samples to high heat. They are sometimes used for driving water out of a hydrated sample before weighing or before an experiment that must be done in anhydrous (no water) conditions. Crucibles can be used with our without a lid and are generally heated over a lab-burner flame.

Crucibles are related to evaporating dishes, larger, lidless,bowl-shaped porcelain dishes used to evaporate liquids from solids.

A large fraction of all of the laboratory porcelain made is manufactured by Coorstek. The company was one of several originally established by Adolph Coors, brewer of Coors® Beer in Golden, Colorado. Turn your piece of lab porcelain over and you'll likely see the familiar Coors® logo.


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