ABSTRACT
Particles of a secondary origin which form by nucleation and subsequent chemical growth will possess size distributions ranging from the finest to the most coarse particles. Optical microscopy is most useful in studying the larger particles that occur in dust specimens, and in this role can only be considered to be useful for obtaining morphological information. Although volatile substances such as water may be lost from the particles that are collected, the remaining residues are sufficient to identify the nature of the particles and their chemical composition. Optical microscopic techniques have been and are still the most inexpensive and practical methods employed to examine aerosol particles. The optical examination of mineral particles is a well-established mineralogical procedure but it is normally confined to the study of particles which are very much larger than those encountered in aerosol samples. The analysis of such X-rays would yield quantitative chemical information, provide a microchemical analysis capability of great importance in aerosol particle characterization.
