... V.C., The Infrared Spectra of Minerals, Mineralogical Society, London, 19 74, 539.28. Griffith, W.P., Advances in the Raman and infrared spectroscopy of minerals, Spectroscopy of Inor-ganic-based ... have proved that the valency of this metal variesaccording to the size of the aerosols. The smallest aerosols (<1.1 µm) and the largest ones (>5.8µm) contain chromium in the hexavalent ... Ni-, Zn-, Cu-, Co-, Al-,and Cd-Cro 4 )Raman results of standard chromium compounds and dust aerosols (8 to 10 µm) collected on the portable impactor are summarized in Table 7 .4 and in Figures...