ABSTRACT
This chapter discusses the physical basis of turbidity measurements and demonstrates how such measurements may be used to infer the scattering cross section of the particles in the solution or the concentration of the scatters in the solution. It also discusses turbidity of pure fluids and shows how certain critical exponents may be determined from such measurements. The chapter provides information on laboratory instruments and the relative trade-offs involved in such instruments. It is well known that even in very pure and well-filtered liquids, in which there are essentially no particles, there is still some reduction in the detected power due to scattering. Highly turbid samples, which transmit very little light, may be difficult to measure using a photodiode. In such cases, the photodiode in the sample arm may be replaced with a photomultiplier.
