The specific gravity of a solid or liquid is the ratio of the density of a substance (completely dense) to the density of pure H2O (999.972 kg/m3) at standard atmospheric pressure and 3.98℃. The specific gravity of gas refers to the ratio of the density of gas to the density of air under standard conditions. The specific gravity of a liquid or solid indicates whether they sink or float in another liquid.

Specific gravity is a dimensionless quantity, that is, specific gravity is a unitless value, which generally changes with temperature and pressure. Specific gravity is abbreviated as S.G. Specific gravity is defined as the ratio of the completely dense weight of a dry object (without pores) to the weight of the same volume of pure water at 4℃. For example, the specific gravity of gold is 19.3, and that of mercury is 13.55.

Application of specific gravity

geology

Geologically, the ratio of the weight of minerals to the weight of water with the same volume at 4℃ is called the specific gravity of minerals. If the chemical composition of the mineral contains elements with large atomic weight or the atoms or ions in the internal structure of the mineral are densely arranged, the proportion is heavy; On the contrary, the specific gravity is small. The specific gravity of most minerals is between 2.5 and 4; Some heavy metal minerals are often between 5 and 8; Very few minerals (such as platinum group minerals) can reach 23.

petroleum

Specific gravity refers to the specific gravity of API gravity or API specific gravity, which is the measurement data for comparing liquid petroleum and water. If the API gravity of liquid petroleum is greater than 10, it is lighter than water and floats on water; If it is lower than 10, it is heavier. Therefore, the specific gravity of API can be regarded as the relative density of liquid oil and water.