Mössbauer spectroscopy analysis of valence state of iron in historical documents obtained from the National Library of South Africa

Documents of historical and cultural value are under constant risk of deterioration by acid hydrolysis and catalytic oxidation. The assessment of this risk of degradation is necessary in order to prepare for the conservation and preservation of such documents. The risk of oxidative degradation of four historical documents obtained from the National Library of South Africa and one sample from the Timbuktu manuscripts was assessed by determining the valence states of Fe in the samples using Mössbauer Spectroscopy (MS). The pH levels of the samples were also determined using the Abbey pH pen. It was found that all the samples were acidic, indicating that acid hydrolysis is occurring in all samples. One sample (Wildsport of Africa) had both Fe2+ (21%) and Fe3+ (79%); all the other samples had only Fe3+. The detection Fe2+ in the Wildsport of Africa sample shows that oxidative degradation is also occurring in this document. The results also show for the first time ever that MS can be used to determine the valence state of trace amount of iron in paper.