Methods are described which allow both the estimation of aluminium not seen by continuous wave techniques and the amounts of the NMR spectra lost in pulsed work. The use of pulsed NMR techniques further complicate the quantitative measurement of 27 Al NMR spectra, especially when high resolution NMR spectrometers are used for this purpose. It is showns that the so called 'invisible' aluminium atoms seen by recent workers are completely consistent with known continuous wave NMR studies of the 27 Al NMR spectra of high surface area aluminium oxides. This paper discusses the quantitation of 27 Al NMR spectra. Quantification of aluminium-27 NMR spectra of high-surface-area oxides ГўвЂ“Вє Maghemite NMR spectral broadening due to various iron sites and supertransferred hyperfine field. ГўвЂ“Вє Strong agreement between predicted spectra and published spectra taken in applied magnetic fields. ГўвЂ“Вє Assignment of NMR spectral components based on crystallographic analysis of unique iron sites. Highlights: ГўвЂ“Вє Analysis of 57 Fe NMR of maghemite based on vacancy ordering and nearest neighbour vacancies. The broadness of the published NMR lines has been explained by calculations of the magnetic dipole fields at the various iron sites and consideration of the supertransferred hyperfine fields. The spectral components have been assigned to particular configurations and excellent agreement obtained in comparing predicted spectra with published spectra taken in applied magnetic fields. International Nuclear Information System (INIS)ДЄll possible iron environments with respect to nearest neighbour vacancies in vacancy-ordered and vacancy-disordered maghemite have been evaluated and used as the foundation for a crystallographically-based analysis of the published NMR spectra of maghemite. Crystallographically-based analysis of the NMR spectra of maghemite

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