The determination of the density of a substance. In the case of minerals several techniques are available. (a) Using a Jolly’s spring balance, the mineral is first weighed in air and then immersed in water and reweighed. The density is calculated by comparing the two weights. (b) The Berman balance is a very sensitive torsion balance used for determining the density of small fragments of minerals, based on the same principle as the Jolly balance. (c) A pycnometer is used to determine the density of soils or powdered minerals. It consists of a small bottle fitted with a ground-glass stopper with a capillary opening. The specimen is placed in the pycnometer, weighed, and then the bottle is filled with water and reweighed. (d) Heavy liquids can also be used. Liquids which are relatively dense, such as bromoform (sp. gr. 2.89) and methylene iodide (sp. gr. 3.33), may be mixed with acetone (sp. gr. 0.79) to produce a series of liquids of known density. If a mineral is introduced into one of these liquids and it neither rises nor sinks its density is the same as that of the liquid. These heavy liquids are often toxic, and great care must be taken when using them. Gloves and face masks should always be worn. See also counterpoised beam balance.