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Reprint

International Symposium
August 20-21, 1992
Cambridge, MA

Sponsored by:
Chemical Manufacturers Association
Crystalline Silica Panel

Co-Sponsored by:
American Industrial Hygiene Association
Analytica Chimica Acta
U.S. Bureau of Mines
Ceramic Industry Magazine
Clay Minerals Society
Occupational Safety and Health Administration
Sorptive Minerals Institute

Evaluation of the Detectability and Quantification of
Respirable Crystalline Silica by X-ray Powder Diffraction
Methods

by

Deane K. Smith
Department of Geosciences and
Materials Research Laboratory
The Pennsylvania State University
University Park, Pennsylvania 16802, USA


Abstract

Introduction
Crystalline Silica in the Industrial Environment
Forms and Sources of Crystalline Silica
Literature Review
Principles and practices of QXRPD
Basic Theory and Its Significance in Silica Determinations
Advantages of QXRPD for Crystalline Silica
Problems of QXRPD
The Integration of Diffraction Peaks by Profile Fitting
Samples and Sampling
The Nature of Samples for X-ray Diffraction Analysis
Crystallite Statistics
Particle Size Effects and Amorphous Layers
Standard Procedures
The Analysis of Bulk Samples
Quartz Analyses Using Membranes Filters
Comparisons of Filter Methods
Calibration
Discussion
Evaluation of QXRPD as a Tool for Silica Analysis
Specific Problems in QXRPD Analysis
Comments on Standardized Procedures
Bulk Sample Analysis
The Cristobalite Problem
The Importance of Tridymite and Other Silicas
The Need for Standard Silica Samples
Calibration Curves and Correction Factors
Detection Limits
 Recommendations
Modifications to the Diffractometer for Quantification
Modifications in Sampling
Other Recommendations
Summary

Acknowledgements

References and Bibliography

Appendix