Surface tension of mercury

According to Rootare [42,66] the best of the published values for the surface tension of mercury is given by Roberts [67] who found a value 

N m-1 °C 1. He attributes the wide variation in published results to the use of contaminated mercury. 

0 =140 [equation (4.2)] the values of y at 25 C and 50°C yield calculated radii of 3.72 nm and 3.68 nm respectively. The effects of temperature on surface tension values are found to have a minimal effect on measured pore stracture and pore rize distribution [59]. 

A higher error in / values is caused by neglecting the curvature of the meniscus in the pores. The following correction has been suggested [68]  

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Some data obtained by Nicholas et al. [150] are given in Table III-3, for the surface tension of mercury at 25°C in contact with various pressures of water vapor. Calculate the adsorption isotherm for water on mercury, and plot it as F versus P. 

Because of the large surface tension of liquid mercury, extremely large supersaturation ratios are needed for nucleation to occur at a measurable rate. Calculate rc and ric at 400 K assuming that the critical supersaturation is x = 40,000. Take the surface tension of mercury to be 486.5 ergs/cm. ... 

In 1873, Gabriel Lippmann (1845-1921 Nobel prize, 1908) performed extensive experiments of the electrocapiUary behavior of mercury and established his equation describing the potential dependence of the surface tension of mercury in solutions. In 1853, H. Helmholtz, analyzing electrokinetic phenomena, introduced the notion of a capacitor-like electric double layer on the surface of electrodes. These publications... 

G. Lippmann introduced the capillary electrometer to measure the surface tension of mercury (Fig. 4.10). A slightly conical capillary filled with mercury under pressure from a mercury column (or from a pressurized gas) is immersed in a vessel containing the test solution. The weight of the mercury column of height h is compensated by the surface tension according to the Laplace equation... 

Electrocapillarity is the measurement of the variation of the surface tension of mercury in (usually) aqueous electrolyte with applied potential. The surface tension, y, of an interface relates to the surface free energy, C, by the expression ... 

A typical plot of the surface tension of mercury vs. the applied potential is shown in Figure 2.1(d), which shows the y/V plot for a IM HCI solution. Clearly, the form of the plot is an inverted parabola, suggesting that y at — V2. 

Figure 4.15 Surface tension of mercury in the presence (dashed line) and in the absence (solid line) of an aliphatic compound (schematic).

The surface tension of mercury in the presence of the vapour at various partial pressures was measured by the drop weight method. The following values were obtained for the surface tensions of mercury in the presence of vapours of methyl acetate, water and benzene at various partial pressures at 26 —27° C. 

According to Iredale the true surface tension of mercury in contact with its own vapour at 18° is ca. 476 dynes per cm., and that normally there exists some material which rapidly lowers the tension, presumably by adsorption. On increase of the gas pressure however, this material is displaced from the mercury surface and the surface tension rises again. ... 

For natural dropping, the flow rate of Hg will be dependent on the column height. It is also dependent on the depth of the tip s immersion in the solution and on the work needed to expand against the surface tension of mercury. It is thus possible to express the effective pressure as... 

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. 

Mercury is a nonwetting liquid that must be forced to enter a pore by application of external pressure. The surface tension of mercury causes mercury to bridge the openings of pores, cracks, and crevices until sufficient pressure is applied to force entry. For example, at atmospheric pressure, mercury will resist entering... 

Fig. 1.7 Surface tension of mercury in contact with aqueous solutions of the salt named. T = 291 K. Abscissas are measured relative to a rational scale in which the potential difference between the mercury and a capillary-inactive electrolyte is arbitrarily set equal to zero at the electrocapillary maximum. Taken from [19] with permission...

Similarly, the surface tension of mercury is made up of dispersion and metal bond contributions ... 

Although the experimental conditions for diffusion-controlled current may be in effect for a polarographic measurement, the resultant current may not be controlled purely by diffusional processes. A convenient way to test whether this is true is to vary the height of the mercury column. The fluid flow characteristics of a capillary with a hydrostatic head are such that the diffusion current is directly proportional to the square root of the height of the column (small corrections for the surface tension of mercury on glass and for the hydrostatic backpressure of the water-immersed portion of the capillary are necessary for the most precise measurements)... 

The poly-[HIPE] sample intrusion mercury porosimetry study reported in Figure 4.67 was carried out in a Micromeritics, Atlanta, GA, USA, AutoPore IV-9500 automatic mercury porosimeter.1 The sample holder chamber was evacuated up to 5 x 10-5 Torr the contact angle and surface tension of mercury applied by the AutoPore software in the Washburn equation to obtain the pore size distribution was 130° and 485mN/m, respectively. Besides, the equilibration time was 10 s, and the mercury intrusion pressure range was from 0.0037 to 414 MPa, that is, the pores size range was from 335.7 to 0.003 pm. The poly-(HIPE) sample was prepared by polymerizing styrene (90%) and divinylbenzene (10%) [157],... 

The surface tension of water at 20°C (72.8 dyne cm-1) is higher than the surface tension of chloroform (27.14 dyne cm-1) but lower than the surface tension of mercury (476 dyne citT1). This indicates that the attractive forces between the water molecules are stronger than the attractive forces between the chloroform molecules but weaker than the attractive forces between the mercury molecules. 

Fig. 3.2 The experimental arrangement for measurement of surface tension of mercury by Lippmann s method.

Mercury has a high density (13.546 g cm" at 20 °C) and a wide liquid range (mp -38.9 °C bp 357) over most of which its volume expands uniformly. In addition, the high surface tension of mercury keeps it from sticking to glass surfaces. These properties have contributed to its use in an impressive number of laboratory applications. For a metal, mercury has an unusually high electrical resistivity or specific resistance (95.8 J,S2 cm), and this property enables it to be used as an electrical standard. Of all the common metals, only bismuth has a higher resistivity. 

MIP experiments were performed on CE Instruments PASCAL 140 and 440 porosimeters, which operate in the pressure range of vacuum to 400 kPa and 100 kPa to 400 MPa, respectively. Prior to the intrusion experiments the samples were degassed in vacuum at 625 K for 16 h. The PSD was determined from the Washburn equation, taking the surface tension of mercury being 480 N m h The contact angle was experimentally determined as described above. 

Mercury s atomic number is 80 and its atomic weight is 200.59. It has a boiling point of 674°F (356.7°C) and a melting point of -38°F (-38.89°C). Mercury is stable (it does not react) in air and water, as well as in acids and alkalis. The surface tension of mercury is six times higher than that of water. Because of this, even when mercury is in liquid form, it does not wet the surfaces it contacts. 

The pore size distribution is derived, assuming a cylindrical pore model, from the intrusion volume-pressure curve using the Washburn law dp = -Ay cos0) / P, where y is the surface tension of mercury (484 mN/m), 6 the solid/mercury contact angle (130°) and P the pressure exerted by the mercury. 

In the 1930s many workers investigated the adsorption of vapors on liquid mercury surfaces, which reduced the surface tension of mercury considerably from 488 mNnT1. However, it is a very difficult task to prepare pure fresh liquid mercury surfaces for such experiments, and there is great confusion in the data reported. On the other hand, many papers were published on the adsorption of solutes over organic solvent sub-phases. In general, the decrease in surface tension of the organic solvent with the increase in solution concentration was less than the results obtained for water sub-phases. 

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