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Photometric On‐line Measurement of Surface Area of Powders
Author(s) -
Leschonski Kurt,
Boeck Thomas
Publication year - 1985
Publication title -
particle and particle systems characterization
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.877
H-Index - 56
eISSN - 1521-4117
pISSN - 0934-0866
DOI - 10.1002/ppsc.19850020116
Subject(s) - attenuation , extinction (optical mineralogy) , optics , absorption (acoustics) , aerosol , line (geometry) , materials science , attenuation coefficient , volume (thermodynamics) , physics , geometry , meteorology , mathematics , quantum mechanics
Amongst the well known methods to measure surface area of particulate matter, preferably dry powders, only photometric methods can be used on‐line. The basic equation for the photometric measurement of surface area is Lambert‐Beer's law, which describes the attenuation of light (extinction) due to the presence of particles in a light beam. The attenuation being dependent not only on the size distribution of the particles in the light beam but also on their volume concentration. Since both effects alter the attenuation simultaneously the solids volume concentration has to be measured independently of the attenuation in a true on‐line system. The instrument developed combines the extinction of white light with the absorption of γ‐rays. Since the absorption of γ‐rays demands more particles in the measuring zone than the attenuation of light, an aerosol stream of rectangular cross section has been used which allows the simultaneous measurement of extinction and γ‐ray absorption. Apart from a brief description of the theoretical background of the instrument experimental evidence will be given of its suitability for on‐line application [1, 2].