Determination Of Aluminum By Kinetic-Potentiometric Method

Kinetic analysis is a kind of non-equilibrium-state determination in which the rate of a chemical reaction in the middle of the reaction is determined. The rate of the reaction has a function relationship with the consistency of the catalyst or the reactants. A kinetic-potentiometric method is described for the determination of aluminum(III) based on monitoring its coordination reaction with fluoride using a fluoride ion-selective electrode(ISE). The initial rate of the reaction is proportional to the concentration of aluminum present in the solution. The kinetics of the coordination reaction is separately studied in acidic solution at pH 1.0, 2.0, 3.6, 4.7 when the concentration of aluminum trichloride solution changes between 0.0100mol/L and 0.1000mol/L and the concentrations of sodium fluoride solution are 8.3 × 10^-6,8.3 × 10^-5,8.3 × 10^-4,8.3 × 10^-3 mol/L. The result shows that the most applicable range of pH is 1～2, and the most applicable range of the ratio of total aluminum with total fluoride is 1.6:1～8:1, 16:1～80:1 and 80:1～800:1 when the concentration of aluminum trichloride solution changes between 0.0100mol/L and 0.1000mol/L,. The kinetics of the coordination reaction is also separately studied under different temperature of 10℃, 20 ℃, 30℃, 40 ℃. The result shows the most applicable range of temperature is 10℃～20℃. This kinetic-potentiometric method is used to the determination of the imitative samples of aluminum. The deviations of the results are all about 5%. The interference of Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ to the determination of aluminum using the kinetic-potentiometric method is also discussed. According to the result of the experiment, the interference of Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ is slight, and the presence of Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ doesn't have strong influence to the determination of aluminum. The contents of aluminum of two kinds of zinc-aluminum alloys are determined. The results are compared with those of the contrast experiments, and the relative deviations are 9.7% and -6.7%.