Mixing processes are frequently characterized with competing chemical reaction schemes. The most popular reaction scheme for continuous flow mixers is the iodide iodate reaction method, which traditionally uses sulfuric acid as proton source for both reactions involved in the scheme. Experimental evidence is provided which indicates that for a quantitative treatment of the experimental data either the experiments need to be carried out with a strong acid such as perchloric acid or the dissociation constants of sulfuric acid need to be included in the models linking the primary experimental results with quantitative measures such as mixing times. Another chemical test reaction system, the acetal cleavage method, traditionally carried out with hydrochloric acid was applied for comparison. In that case, the use of perchloric acid showed no significant impact on the experimental results. (C) 2009 Elsevier Ltd. All rights reserved.