Nephelometry and Turbidimetry: Principle, Theory and Techniques

- Mar 22, 2018 -

After reading this article you will learn about:- 1. Subject Matter of Nephelometry and Turbidimetry 2. Principle and Theory of Nephelometry and Turbidimetry 3. Operating Conditions 4. Instrumentation 5. Experimental Techniques 6. Applications.

Subject Matter of Nephelometry and Turbidimetry:

Nephelometry and Turbidimetry are used for continuous monitoring of air and water pollution. In water, turbidity is monitored whereas in air, smoke and dust are monitored. The techniques are also used in food, beverages and in the determination of molecular weight of high polymers which are settled down on earth from factories. The CO2 can also be determined by this technique.

Neptielommetric analysis is based on measuring the intensity of a luminous flux scattered by solid particles suspended in solution.

Nephelommetric analysis (turbidimetry) is based on measuring the weakening of intensity of a luminous flux when h; passes through a solution containing particles in suspension. The intensity decreases owing to absorption and scattering of light.

Principle and Theory of Nephelometry and Turbidimetry:

The principle of nephelometry and turbidimetry is based on the scattering or absorption of light by solid or colloidal particles suspended in solution. When light is passed through the suspension, part of incident radiant energy is dissipated by absorption, reflection, and reaction while remainder is transmitted.

In fact the measurement of the intensity of transmitted light is a function of the concentration of dispersed phase and this becomes the basis of turbid metric analysis.

This is given in the following diagram 5:

It is very important to note that in nephelometry incident and scattered light are of same wavelength whereas in fluorimeter (in fluorimetry) scattered light is of longer wavelength than incident light.


For turbidmetric measurements the transmitted intensity I can be determined from the equation.

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