My research involves developing an experimental device that uses the attenuation of laser light to measure particle concentration. Real-time measurements of particle concentration within gas-particle flows is needed for the development of a novel process for removing mercury from the flue gases of coal-fired power plants, called a virtual sorbent bed (VSB) . The Powdered Activated Carbon (PAC) particles are suspended in an optically accessible chamber and a HeNe laser beam is directed through the suspensions. The attenuation of the laser beam, as measured by a receiving photodiode positioned opposite the laser, provides a measure of the degree of light absorption and scattering produced by the particles in the suspension. Calibration of the experiment includes accurately accounting for particle deposition on the optical windows through which the laser beam passes, as well as particle size and size distribution effects on the attenuation of the beam.