GENERATION AND USE OF 3 TYPES OF IRON-OXIDE AEROSOL

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Abstract
Three distinct submicrometric aerosols of iron oxide can be reproducibly generated by combustion of iron pentacarbonyl vapors under varying conditions. Each aerosol was sized with a concentric aerosol spectrometer and was examined with an EM; the specific surface area of each aerosol type was determined. The feathers hematite has a mass median aerodynamic diameter (MMAD) of 0.17 .mu.m and a large surface area because it is an agglomerate of units 0.005 .mu.m in diameter. The birdshot hematite has a MMAD of 0.31 .mu.m, but has a smaller surface area because the subunits are 0.03 .mu.m in diameter. The 3rd aerosol, gamma-oxide, has a MMAD of 0.73 .mu.m and has crystalline subunits 0.2 .mu.m in diameter; it is a magnetic form of hematite, .gamma.-Fe2O3. These aerosols are well suited for studies of deposition and clearance in animal lungs because the particles can be visualized in light microscopy and EM and can be quantified colorimetrically. The magnetic properties of .gamma.-Fe2O3 permit enhancement of deposition and noninvasive detection.