Publisher Summary The actual density of a solid substance, even of a relatively small individual crystal, may be measured by determining the density of an inert liquid mixture in which the crystal remains just suspended. A crystal of sodium nitrate (2260 kgm-3) could be floated in about 50 mL of bromoform in a suitable flask—taking care that no air bubbles are attached—and then made to achieve the “just suspended” state by slowly adding chloroform from a burette. At this point, the crystal density may be assumed to be equal to that of the liquid mixture, which can readily be estimated. Solid densities have very small temperature dependence, but this can be ignored for industrial crystallization purposes.