Using nephelometry, you measure the scattered light that is created after a light beam meets a particle. If a substance is completely dissolved in solution then there will be nearly no scattered light leading to a low nephelometric value. But if the solubility limit is reached and the substance starts to precipitate, the light will be scattered strongly leading to a high nephelometric value. This measurement technique is opposite to absorbance but is very well suited to monitor microbial growth. Other applications that greatly benefit from nephelometry include drug solubility screening, bacterial and fungal growth kinetics, determination of precipitation of particles in solution (e.g. immunoprecipitation, protein precipitation), quantification of macromolecules, toxin/antitoxin flocculation in serum and polymerization reactions just to mention a few.
BMG LABTECH offers a microplate reader dedicated to Nephelomerty, NEPHELOstar. For more information see: http://www.biocompare.com/ProductDetails/146087/NEPHELOstar-Microplate-Nephelometer.html?