Specific gravity

Specific Gravity

Specific gravity (pronounced: spuh-SIF-ik GRAV-i-tee) is a concept used in various scientific fields, including physics and medicine. It is a measure of the relative density of a substance as compared to the density of another reference substance.

Etymology

The term "specific gravity" comes from the Latin words "specifus" meaning "certain kind" and "gravitas" meaning "weight".

Definition

In medicine, specific gravity is often used in the analysis of bodily fluids, such as urine or blood. The specific gravity of a fluid is a measure of the amount of solutes (dissolved substances) present in it. It is a unitless measure, as it is a ratio of the density of the fluid to the density of a reference fluid (usually water at 4 degrees Celsius, which has a density of 1 g/cm^3).

Related Terms

Density: The mass of a substance per unit volume. It is often used as the reference in specific gravity calculations.
Solute: A substance that is dissolved in a solution.
Solution: A homogeneous mixture of two or more substances.
Urine: A liquid by-product of the body secreted by the kidneys and excreted through the urethra.
Blood: A body fluid in humans and other animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells.

Medical Applications

In medicine, the specific gravity of urine is a commonly measured parameter in urinalysis. It can provide valuable information about a patient's hydration status and kidney function. For example, a low specific gravity can indicate overhydration or kidney disease, while a high specific gravity can suggest dehydration or other conditions.

The specific gravity of blood is also sometimes measured, particularly in the context of blood doping tests in sports medicine. A high specific gravity of blood can indicate the presence of performance-enhancing substances.