THE INFLUENCE OF IRON ON PROTON NUCLEAR-MAGNETIC-RESONANCE MEASUREMENTS OF COALS

The extent to which paramagnetic iron ions contained in coals and solid coal residues can affect the proton nuclear magnetic resonance (**1H nmr) properties is investigated. It is demonstrated that these dispersed paramagnetic ions even in large concentrations do not have a significant quantitative effect on proton spin populations determined by high-power pulsed **1H nmr measurements. It is further shown how magnetic ordering of such ions, which may occur naturally or be established during pyrolysis from iron pre-existing in other forms, can result in significant proportion of the ph proton populations being 'nmr invisible'.