The Density of Rock Salt and Calcite

Crystals as perfect as could be secured were obtained from a variety of sources, and densities were measured by weighing them when suspended in paraffine oil or water respectively. The weights were calibrated and correction was made for the buoyancy of the air. The measurements are accurate to.2 mg ${\mathrm{cm}}^{-3\mathrm{}}$ for rock salt and to.1 mg ${\mathrm{cm}}^{-3\mathrm{}}$ for calcite. Variations in density were observed between different parts of the same crystal, as well as between different crystals, which are larger than the experimental error. The estimated uncertainty of the mean density is taken as the probable variation of the individual samples from the mean density. The mean result for 7 good crystals of rock salt is 2.1632±.0004 gm ${\mathrm{cm}}^{-3\mathrm{}}$, and for 6 crystals of calcite, 2.7102±.0004 gm ${\mathrm{cm}}^{-3\mathrm{}}$, at 20°C.