The speciation diagrams are suggested as a reasonable tool for explanation of processes occurred during simulated redox titration, where K2Cr2O7 solution is added into acidified (H2SO4) solution of KI. The related speciation curves log [X-i(zi)] = f(i) (Phi) for all interesting species Xzi i of the system, and the E = E(Phi) and pH = pH(Phi) relationships (Phi-fraction titrated) are plotted and discussed. The calculations made for this purpose are performed in accordance with principles of the Generalized Approach to Electrolytic Systems (GATES) with Generalized Electron Balance (GEB) involved, and realized with use of iterative computer programs offered by MATLAB. The reactions proceeding in this system can be formulated together with their efficiencies, at any stage of the titration. The stoichiometry is considered as the derivative concept when put in context with GATES/GEB. (C) 2015 Elsevier Ltd. All rights reserved.