Nephelo is derived from the Greek word "nephele," meaning clouds. Nephelo refers to the quality in water or a sample that defines its cloudiness or clarity. Most of the time in the biological and chemical sciences, "nephelo" is used in conjunction with another term, particularly nephelometric.
Nephelometrics use a variety of test measures to determine cloudiness of water or liquids. The typical method is passing light through the liquid and measuring how much is reflected from the particles suspended in it. This is a surprisingly sensitive measurement. After calibrating for light lost to the container, light-measuring nephelometrics can pick up even the slightest cloudiness in water.
To get the most accurate readings from a nephelometer, the sample should be analyzed immediately to prevent settling and other quality changes. Sample containers should be clean and undamaged and oiled with silicon to minimize imperfections. Samples with a lot of color often get readings that are inaccurate, as color absorbs light. High quantities of air bubbles can also skew readings, as will free carbon in the sample.
Vibrations and electric fields will affect the reading. Vibration increases light scattering, so a normal sample may register high on a nephelometer. Electiric fields affect often-charged particles, and can cause nephelometric readings to be either too high or low.
Web Resources On Nephelo
Book Resources On Nephelo
Turbidity in the Aquatic Environment by Charles Grady Wilber
A Study of Low-Level Turbidity Measurements by Raymond D. Letterman (Ed)