filtrate

Filtrate is the liquid that passes through a filter during filtration. It consists of the solvent and any solutes small enough to traverse the filter medium, while the solids left on the filter form the residue or retentate. The composition of a filtrate depends on the filter’s pore size, material, and the properties of the mixture being filtered.

Filtrates are encountered in many scientific and practical contexts. In laboratory settings, the filtrate is the portion analyzed for dissolved substances after solids are separated. In everyday life, the term can describe the beverage that passes through a coffee or tea filter. In environmental and industrial processes, filtrates characterize the clarified liquid produced during water treatment or chemical purification, and in medical contexts such as dialysis the filtrate refers to the fluid that crosses a semipermeable membrane.

In physiology, the term is used for the plasma ultrafiltrate produced by the kidneys, known as the glomerular filtrate. This fluid contains water, electrolytes, glucose, and small solutes, but usually lacks large proteins and cells. The exact composition varies with filtration rate and membrane selectivity. The word filtrate comes from Latin filtratus, meaning “filtered,” and is used both as a noun and a verb; the material that remains behind is called the retentate or residue.