Fig. 1. (a) Effect of added H₂O₂ volume on the efficiency of organic C removal from Welsh carbonate-free Madryn soil (•, 5.1% C) and Bodrwyn soil (, 4.3% C) using 6%(wt/wt) H₂O₂. (b) Organic C removal efficiency from bulk soils with increasing H₂O₂ concentration. Soils contained between 1.3 and 6.5% organic C. Sixty milliliters H₂O₂ were added equivalent to 0.08 g C. The samples were heated gently then boiled (data adopted from McLean, 1931a, 1931b).