Curve of Mercury

The isotherms of N2 adsorption on MCM-41 and two samples of SBA-15 synthesized at different temperatures are reported in Fig. 1. The curves of mercury intrusion-retraction... 

Figure 2.21 Effect of adsorbed camphor on the electrocapillary curve of mercury and on the polarographic reduction of Cu(II)-EDTA. (A) Electrocapillary curve of camphor in acetate buffer a, without b, with 3 x 10-4 M camphor. (B) Polarograms of a solution containing 0.009 M EDTA, 0.001 M Cu(II), 0.1 M acetate buffer, pH 4.5 a, without b, with 3 x 10 4 M camphor. [Adapted from Ref. 14, p. 91.]...

Fundamental knowledge about the behavior of charged surfaces comes from experiments with mercury. How can an electrocapillarity curve of mercury be measured A usual arrangement, the so-called dropping mercury electrode, is shown in Fig. 5.2 [70], A capillary filled with mercury and a counter electrode are placed into an electrolyte solution. A voltage is applied between both. The surface tension of mercury is determined by the maximum bubble pressure method. Mercury is thereby pressed into the electrolyte solution under constant pressure P. The number of drops per unit time is measured as a function of the applied voltage. 

If we measure electrocapillary curves of mercury in an aqueous medium which contains KF, NaF, or CsF, then we observe that the typical parabolas become narrower with increasing concentration. Explanation With increasing salt concentration the Debye-length becomes shorter, the capacity of the double layer increases. The maximum of the electrocapillarity curve, and thus the point of zero charge (pzc), remains constant, i.e., neither the cations nor fluoride adsorb strongly to mercury. 

Figure 5.4 ElectrocapiUary curves of mercury measured in different aqueous electrolytes at 18°C. The zero of the applied electric potential was chosen to be at the maximum of the electrocapillary curve for electrolytes such as NaF, Na2S04, and KNO3, which do not strongly adsorb to mercury. Redrawn after Ref. [59].

Other new tables include the Melting Curve of Mercury, Enthalpy of Hydration of Gases, and Electrical Resistivity of Graphite Materials. Several other tables have been updated with recently reported data. 

X 10" respectively. When pilocarpine is dissolved in excess of acid and back titrated with sodium hydroxide, a sharp break in the titration curve is observed at pH 4.31 (99). The pH of a solution of pilocarpine hydrochloride, measured electrometrically, is 4.44 at 18° (100). The influence of pilocarpine on the electrocapillarity curve of mercury has been determined by M. Gouy (101). 

The meticulous study of the effects of adsorption of organic compounds on the electrocapillary curves of mercury, which was accomplished by Frumkin at the Karpov Institute, led to the discovery of the famous isotherm that now bears his name (the Frumkin isotherm [7]). Whereas the Langmuir isotherm was based on the somewhat naive assumption that adsorbed species did not interact, Frumkin showed that such interactions were often very strong indeed. In addition, Frumkin combined his results with an electrical model of two capacitors in parallel, which later became the prototype for many multistate models. 

In 1939, while carrying out ac measurements in dilute electrolyte solutions, Frumkin and M. A. Vorsina [12] discovered an unexpected minimum in the differential capacitance curves of mercury. They correctly associated this minimum with the behavior of the diffuse part of the double layer in the vicinity of the zero charge potential. 

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