16 DIY Science: Illustrated Guide to Home Chemistry Experiments
beakers are also more difficult to clean thoroughly and may
have to be discarded in situations where a glass beaker could
simply be washed.
Most beakers are graduated with painted, etched, or raised
lines to indicate the approximate volume the beaker contains
at various fill levels. For example, the 250 mL beaker shown in
Figure 3-3 has markings every 25 mL. Graduated beakers are
typically accurate to within ±5%, and can be used to measure
and dispense liquids when high accuracy is not required.
Laboratory beakers are available in two styles. Berzelius
beakers, also called high-form beakers are tall and slender.
Griffin beakers, also called low-form beakers, are shorter and
squatter. For a home laboratory, either style is fine.
If you use a beaker for short-term storage of a solution, cover it
to prevent evaporation or contamination. Use a watch glass, an
ordinary piece of glass, or plastic film wrap. If you use a beaker
to boil a solution, always add a boiling chip or leave a stirring rod
in the beaker to prevent the solution from boiling over, as shown
in Figure 3-4.
A well-equipped home chemistry lab should have a good
selection of beakers, most mid-sized, but with a few larger
and smaller ones for special purposes. The 150 mL or 250 mL
size is the most useful for most home labs. Many laboratory
equipment suppliers sell assortments of various-size beakers at
a discounted price. Many also sell boxes of six to twelve beakers
of the same size at a significant discount relative to the single-
unit price.
fLASSk
Like beakers, flasks are used routinely for storing, mixing,
measuring, heating, and boiling liquids. The primary difference
is that beakers have wide mouths and flasks have narrow
mouths, which means it’s easy to seal a flask using a rubber
or cork stopper. Because they are easily sealed, flasks are
commonly used as reaction vessels and for constructing various
apparatuses such as gas-washing bottles, gas generators,FIGURE 3-3: A standard laboratory beaker FIGURE 3-4: Use a stirring rod to prevent boiling over
BRSAE kE vERSUS fLASkS
We use beakers and flasks pretty much interchangeably.
In effect, a beaker is just a wide-mouth flask, and a flask
a narrow-mouth beaker. Flasks are better for swirling or
heating solutions, when the container must be sealed or
is part of an apparatus, or when the contents are volatile.
Beakers make it easier to add large amounts of solids to
a solution, and their lips make them more convenient for
pouring, filling burettes, and so on.
We wondered if there were other good reasons to use
one or the other in particular situations, so we asked
our advisor Dr. Paul Jones, who is an organic chemistry
professor. He confirmed our thoughts on the matter, and
added that he seldom uses beakers in his labs, but instead
uses Erlenmeyer flasks almost exclusively. Paul added,
only partially in jest, that he uses flasks when he cares
about what they contain and beakers when he doesn’t.
Which is probably pretty good advice.