1. Density and relative density Density refers to the mass contained in the unit volume of a substance. The unit is milligram / m3 (mg / m3) or kilogram / m3 (kg / m3) or gram / cm3 (g / cm3). Relative density refers to the ratio of the density of a substance to the … Continue reading The most complete collection of 60 performance test methods for non-metallic materials in history