Mercury-displacement method

A helium-mercury displacement method is sometimes used to check the pore volume obtained from the adsorption-desorption isotherm at the saturation pressure (Ries, Van Nordstrand, Johnson, and Bauer-meister, 50). The helium measurement which gives the solid volume and solid density is obtained by means of a miniature isotherm type apparatus. This part of the determination is essentially the same as that described by Smith and Howard (58) and Schumb and Rittner (55). Mercury displacement yields the pellet volume and pellet density and is measured volumetrically by means of a mercury buret attached directly to the same sample bulb in which the helium measurement is performed. The difference between the pellet volume and the solid volume is obviously the pore volume. 

A mercury displacement method based on enhancing the disproportionation reaction of mercurous ion solution by SO2 was utilized for the detection of SO2 (86). 

The usual method to measure the gap volume between particles is Mercury-Displacement Method, which is because mercury can fill the free space between particles and does not enter into the pores of particles. The density measured by this method is also called as false density of particle. 

Other Methods, for Quality Control (Ash Content, Moisture, Bulk or Apparent Density, Specific Gravity by Mercury Displacement, and Solidification Point)... 

The particle density is the weight of a unit volume of solid, including the pores and cracks (Mahajan and Walker, 1978). The particle density can be determined by any of three methods (1) mercury displacement (Gan et al., 1972) (2) gas flow (Ergun, 1951) and (3) silanization (Ettinger and Zhupakhina, 1960). 

Another method of determining porosity involves measuring the density of coal by helium displacement and by mercury displacement (see Section 6.1). Thus, the porosity of coal is calculated from the relationship... 

It is by far the simpler method, gives a purer product, and is to be preferred to the displacement method. The directions given under procedure A are based essentially upon the results obtained by G. MePhail Smith and A. C. Bennett and involve the electrolysis of a saturated solution of barium chloride using a mercury cathode. The displacement method is given as an optional procedure. 

A more accurate procedure is the helium-mercury method. The volume of helium displaced by a sample of catalyst is measured then the helium is removed, and the volume of mercury displaced is measured. Since mercury will not fill the pores of most catalysts at atmospheric pressure, the difference in volumes gives the pore volume of the catalyst sample. The volume of helium displaced is a measure of the volume occupied by the solid material. From this and the weight of the sample, the density of the solid phase, P5, can be obtained. Then the void fraction, or porosity, of the particle, p, may be calculated from the equation... 

The porous, metal-modified, shaped silica catalysts obtained as above are novel and unique products. They consist essentially of the amorphous silica modified with the added metal. They have a density of from 1 to 2g/cm. In these instances where the catalyst is in the form of irregular shaped pieces, the density of the individual pieces can be determined by the method of mercury displacement in an accurately calibrated pycnometer as described by M. Burr, Roczniki Chemie, 31,293 (1957). 

Various methods are available for determining the density of a phase, many of them based on the measurement of the mass of a fixed volume or on a buoyancy technique. Three examples are shown in Fig. 2.4 on the next page. Similar apparatus may be used for gases. The density of a solid may be determined from the volume of a nonreacting liquid (e.g., mercury) displaced by a known mass of the solid, or from the loss of weight due to buoyancy when the solid is suspended by a thread in a liquid of known density. 

Electrochemical reduction of iridium solutions in the presence azodye (acid chrome dark blue [ACDB]) on slowly dropping mercury electrode is accompanied by occurrence of additional peaks on background acetic-ammonium buffer solutions except for waves of reduction azodye. Potentials of these peaks are displaced to cathode region of the potential compared to the respective peaks of reduction of the azodye. The nature of reduction current in iridium solutions in the presence ACDB is diffusive with considerable adsorptive limitations. The method of voltamiuetric determination of iridium with ACDB has been developed (C 1-2 x 10 mol/L). 

Mercury(II) thiocyanate method Discussion. This second procedure for the determination of trace amounts of chloride ion depends upon the displacement of thiocyanate ion from mercury(II) thiocyanate by chloride ion in the presence of iron(III) ion a highly coloured iron(III) thiocyanate complex is formed, and the intensity of its colour is proportional to the original chloride ion concentration ... 

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