Therefore, the relation between the time of maximum heat flow and proton concentration can not be described with a single exponential function. For perchloric, hydrochloric, and nitric acid, the retardation times reach a maximum and then decrease at higher concentrations. For sulfuric acid, the retardation times continuously increase with acid concentrations yet cannot be fitted with an exponential trend either. Among these four acids, the largest retardation time (up to 35 h) is achieved in the presence of 100 µmol/g CAC of perchloric acid. Nitric acid leads to a maximum of 18 h retardation and hydrochloric acid to 5 h. The retardation power of H 2 SO 4 is comparable to hydrochloric acid up to a proton concentration of 150 µmol/g CAC . Above 150 µmol/g CAC , the retardation power of H 2 SO 4 is higher than hydrochloric acid yet lower than nitric acid over the studied range of proton concentrations. It is striking that the overall retardation time, following sequence H 3 PO 4 > HClO 4