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Balances and Glassware for Solution Preparation

Author(s): David R. Caprette, PhD

Glassware

Beakers are suitable for mixing solutions because they have large open tops into which one can pour solvent or large amounts of dry chemicals. Flasks are a bit easier to handle than beakers are, and the solution is less likely to splash out of a flask. The narrow opening discourages evaporative loss and contamination from the outside. A powder funnel can be used to add dry chemicals to a flask, while a glass funnel can be used to add liquid. To measure liquid volumes of 10 milliters or more, graduated cylinders usually are the practical choice. Cylinders are accurate to perhaps 1% of total volume, which is more than sufficient for most solutions. We seldom need volumetric flasks in biology, since we don't need such a high level of precision.

It is good practice to choose graduated cylinders and containers that are as close as possible to the intended volume of the contents. For example, it is not very accurate to use a 2 liter cylinder to measure out 100 ml of water. The same principle holds for weighing materials. It does not make sense to weigh out one hundredth of a gram of substance in a container that weighs 100 grams.

A magnetic stirring rod is useful when it takes some time for a solute to go into solution, although it is possible to add additional contamination into the solution. Use heat only if a formula calls for it.