This article was featured in Lab Asia - July/August 2008
Turbidity can be described only with limitations as a physical and technical measurement category. The unusual nature of the turbidity measurement in comparison to other parameters can be recognised already in its historical development: Initially a procedure was introduced by Jackson and Whipple around 1900 determining turbidity by means of candlelight under a glass tube. Dilution series of diatomaceous earth (diatomite) with its high level of diatoms were used as calibration standards. The turbidity value was determined visually from the top view. Admittedly a somewhat subjective procedure with the measuring unit of JTU, where 1 Jackson Turbidity Unit corresponds to 1 ppm SiO2. However, this was providing the basis for the development and continuous improvement of turbidity measurement with meaningful results.