Relative density (d) is the ratio of the density of a substance to the density of some reference substance. For liquids or solids it is the ratio of the density (usually at 20 °C) to the density of water at 4 °C. Since one must specify the temperature of both the sample and the water to have a precisely defined quantity, the use of this term is now discouraged. This quantity was formerly called specific gravity.
Generalic, Eni. "Relative density." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
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