Three point method

It was shown later that a mass transfer rate sufficiently high to measure the rate constant of potassium transfer [reaction (10a)] under steady-state conditions can be obtained using nanometer-sized pipettes (r < 250 nm) [8a]. Assuming uniform accessibility of the ITIES, the standard rate constant (k°) and transfer coefficient (a) were found by fitting the experimental data to Eq. (7) (Fig. 8). (Alternatively, the kinetic parameters of the interfacial reaction can be evaluated by the three-point method, i.e., the half-wave potential, iii/2, and two quartile potentials, and ii3/4 [8a,27].) A number of voltam-mograms obtained at 5-250 nm pipettes yielded similar values of kinetic parameters, = 1.3 0.6 cm/s, and a = 0.4 0.1. Importantly, no apparent correlation was found between the measured rate constant and the pipette size. The mass transfer coefficient for a 10 nm-radius pipette is > 10 cm/s (assuming D = 10 cm /s). Thus the upper limit for the determinable heterogeneous rate constant is at least 50 cm/s. 

C.H. Massen, J.A. Poulis, E. Robens Criticism on Jantti s three point method on curtailing gas adsorption measurements. Adsorption 6 (2000) 229-232. 

Fdlner-Feldegg, using a multiple scanning technique incon)orating the three-point method of Nicolson and Ross (Figure 10), has recently demonstrated thin-sample t.d.s. by didectric measurements on alcohols. Figure 17 shows the data for butan-l-ol at 298 K plotted on the con l ... 

Measured intensities are to be divided by LPA in order to make the lines more nearly symmetrical, before determining the line center by the least-squares or three-point method. The function LP/1 is tabulated in [16.3]. 

The flexural strengths (three-point method) of these two unidirectional HMS graphite fiber reinforced TSTR polyimide composites with or without post curing were measured with a universal Instron machine at room temperature and at 316°C. These results are shown in Table II. 

Finally, the presence of a contribution of the ohmic drop to electrode overvoltage becomes more important when one tries to evaluate 1 using the three different versions of the three-point method [43, 44, 45]. In its simplest form, the theory of this method. 

House, J. E., House, J. D. (1983). Thermochim. Acta 61, 211. A description of the three-point method and its applications. 

At a constant L, equation (15.18) describes a quasi-reversible steady-state voltammo-gram of a reduction reaction at the tip. Kinetic parameters can be determined either by fitting steady-state voltammograms to this equation or by using the three-point method (14) and assuming uniform accessibility of the tip surface, as discussed in the previous section. In this way, the kinetics of the fast oxidation of ferrocene at a Pt tip electrode was measured (15). The reproducible standard rate constant value (3.7 0.6 cm/sec) was obtained at different tip/substrate distances (Figure 15.4). Thus, one can check the validity of the experimental results and the reliability of the kinetic analysis. 

Once the bed is constructed, the grounding resistance must be checked for acceptance—a resistance of 2-5 Q. Existing beds should also be checked periodically to detect any changes in the resistance, especially when the soil is dry or the weather is cold. Several methods exist for measuring ground bed resistance, including the three-point method, the fall-of-potential method, and the ratio method. Of these three methods, the fall-of-potential is probably the most widely accepted. For this reason, we will describe only the fall-of-potential method here. 

ISO/DIS 12986-1,2. Carbonaceous materials used in the production of aluminium-prebaked anodes and cathode blocks - Part 1 determination of bending/shear strength by a three-point method. 

DIN 51902-1997. Testing of carbonaceous materials - determination of flexural strength by three-point method - solid materials. 

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