ari widayat - Academia.edu (original) (raw)

Papers by ari widayat

The mathematical bases of the Barnartt and LeRoy three point methods are expounded by introducing... more The mathematical bases of the Barnartt and LeRoy three point methods are expounded by introducing an elementary algebraic identity which allows them to be unified, the difference in the known terms of the resulting equations depending only on the chosen criteria of the points (A&, i(A&)) (k= 1,2,3). These methods have been used to process experimental data on iron in HzS04 solutions at various normalities and 2X, and 1 N H#.04 and HCI solutions, containing commercial inhibitors at various concentrations, at 75°C. All the experimental data were best-fitted over the AE interval [ -35,351 mV with a polynomial of the fourth degree in order to meet the choice criteria for any value of A,!$. Based on the polynomial best-fitting a criterion for checking the goodness of the three point method is suggested. The Barnartt method was applied to analyse artificial data obtained by setting I, = 1 mA cmd2, B, = 40 mV and & = 120 mV, and subjected to arbitrary changes, simulating random or systematic errors, in order to verify its value and reliability. Comparison of the two three-point methods and NOLI analysis shows that the determinations of I,, B, and &are rather satisfactory only for the systems at 25°C. For the systems at 75°C the Barnartt method works properly only as concerns the evaluation of I,, whereas the use of the LeRoy method is more critical. At last, examination of artificial data points out that in some cases the equation of the second degree obtained using the Barnartt method has complex roots.

The mathematical bases of the Barnartt and LeRoy three point methods are expounded by introducing... more The mathematical bases of the Barnartt and LeRoy three point methods are expounded by introducing an elementary algebraic identity which allows them to be unified, the difference in the known terms of the resulting equations depending only on the chosen criteria of the points (A&, i(A&)) (k= 1,2,3). These methods have been used to process experimental data on iron in HzS04 solutions at various normalities and 2X, and 1 N H#.04 and HCI solutions, containing commercial inhibitors at various concentrations, at 75°C. All the experimental data were best-fitted over the AE interval [ -35,351 mV with a polynomial of the fourth degree in order to meet the choice criteria for any value of A,!$. Based on the polynomial best-fitting a criterion for checking the goodness of the three point method is suggested. The Barnartt method was applied to analyse artificial data obtained by setting I, = 1 mA cmd2, B, = 40 mV and & = 120 mV, and subjected to arbitrary changes, simulating random or systematic errors, in order to verify its value and reliability. Comparison of the two three-point methods and NOLI analysis shows that the determinations of I,, B, and &are rather satisfactory only for the systems at 25°C. For the systems at 75°C the Barnartt method works properly only as concerns the evaluation of I,, whereas the use of the LeRoy method is more critical. At last, examination of artificial data points out that in some cases the equation of the second degree obtained using the Barnartt method has complex roots.