Which instrument is used to measure turbidity?

The instrument specifically designed for measuring turbidity in water is the turbidimeter. Turbidity refers to the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye. A turbidimeter works by passing light through a water sample and measuring the amount of light that is scattered by the particles within the sample. This scattering is directly related to the concentration of these suspended particles, allowing for an accurate assessment of the turbidity level.

While a spectrophotometer can measure absorbance in a solution and is sometimes used in water quality testing, it is not specifically designed to measure turbidity. A hydrometer is used to measure the density or specific gravity of liquids, and a nephelometer measures light scattering but is more commonly used in contexts like measuring particles in air. Therefore, the turbidimeter is the most appropriate choice when the objective is to quantify the turbidity of water directly.