ABSTRACT
When radiation crosses over a medium in which solid particles are dispersed, one fraction of them is diffused in all directions giving the impression of turbidity to the “mixture”, the other fraction being transmitted without encountering any dispersed particle. Turbidimetry is the measurement of the intensity of the transmitted radiation by the medium. It is determined along the axis of the incident beam. Light has been lost by absorption, reflection and diffusion. Turbidimetry is adapted to media of strong turbidity in which solid particles are big. Nephelometry or nephelemetry is based on the measurement of the intensity of diffused light, a measurement performed at the right angle of the direction of the initial ray. It is used for the analysis of media of weak turbidity. Numerical relations between the decrease of the intensity of an incident beam and the “concentration” of the solid particles exist for both methods. They are quantitative methods of analysis. Turbidimetry is adapted to media of strong turbidity in which solid particles are big. Nephelometry is used for the analysis of media of weak turbidity.
