NIOSHTIC-2 Publications Search
A Review Of The Wet Chemistry Method (Talvitie) For SiO2.
Proceedings of the Symposium on Silica (March 12-13, 1975, Pittsburgh, Pennsylvania), Industrial Health Foundation, Pittsburgh, Pennsylvania 1976:38-55
A colorimetric method to determine silicon-dioxide (7631869) for industrial hygiene analyses is reviewed. The first method originally developed consists of dissolution of various silicate materials in phosphoric-acid followed by a gravimetric determination of free silica (7631869). Results indicate that of the 39 silicate materials investigated 22 dissolved completely in 12 minutes or less; only 4 required digestion times greater than 20 minutes. The use of the phosphoric-acid digestion method for quartz is also outlined and the method is compared with the sulfuric-acid digestion method and the X-ray diffraction method. The agreement on reported results for all three methods is good. Reproducibility of the phosphoric-acid method is greater if the temperature is controlled between 230 to 240 degrees-C during decomposition of minerals. The colorimetric method developed for total silica facilitates measurement of silica as low 1 microgram. A further improvement of this method has rendered it useful for measuring airborne particulates and free silica. The analytical procedure involved in this improved colorimetric method is presented. In principle, the sample in a series of filters is extracted with perchloric-acid, treated with orthophosphoric-acid, diluted with water at 70 to 80 degrees and filtered; the precipitate is treated with borate, ammonium-molybdate, and 1-amino-2-naphthylsulfonate and the developed blue color is read at 820 nanometers in a colorimeter. The limitations of this method, the governing parameters, and the sources of background silica that affect the sensitivity of the method are described. The applications of this method are illustrated. The method is compared with NIOSH approved X-ray diffraction, infrared spectroscopy, and spectrophotometry.
Chemical-processing; Airborne-dusts; Air-monitoring; Air-contamination; Air-sampling-techniques; Air-flow; Air-samplers; Airborne-particles; Airborne-dusts; Air-monitoring; Silica-dusts;
Proceedings of the Symposium on Silica (March 12-13, 1975, Pittsburgh, Pennsylvania), Industrial Health Foundation, Pittsburgh, Pennsylvania
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division