optical density -->
medical dictionary


1. <chemistry> Absorbance is defined as a logarithmic function of the percent transmission of a wavelength of light through a liquid.

2. <microbiology> This can be used as a measure of the amount of light absorbed by a suspension of bacterial cells or a solution of an organic molecule, it is measured by a colourimeter or spectrophotometer.

Absorbance values are used to plot the growth of bacteria in suspension cultures and to gauge the purity and concentration of molecules (such as proteins) in solution.

See: absorption.

(15 Jan 1998)