Mercury compressibility

The effects of mercury compression and the compressive heating of the hydraulic oil are thermodynamically compensated. Therefore, the need to make blank runs is unnecessary for all but the most exacting analysis. Blank runs made on cells filled with mercury show less than 1 % of full-scale signal over the entire operating range from 0 to 60000psi. 

A value of 140 °C was used for the contact angle of mercury on the solid (0), and the surface tension of mercury (7) was taken as 0.485 N/m. These values correspond to an effective working range for the instrument of 150 pm to 1.7 nm in pore radius. The samples were outgassed at room temperature to a pressure of 50 mtorr (7 Pa) immediately prior to analysis to facilitate filling the penetrometers with mercury. All data were fully corrected for mercury compression with calibrated penetrometers. 

These two instruments are designed to compensate for mercury compressibility thermodynamically by balancing the slight expansion due to compressive heating and the associated change in the hydraulic oil dielectric value with pressure. A cell filled with mercury will indicate a deviation on the volume axis of less than 0.5% of full scale therefore there is no need for a blank run. 

The pressures involved in porosimetry are so high (e.g. 1000 atm = 6-6 ton in" ) that the question as to whether the pore structure is damaged by mercury intrusion naturally arises. This possibility was recognized by Drake, but as a result of several intrusion-extrusion runs at pressures up to 4000 atm on a number of porous catalysts Drake concluded that any deformation caused by compression was elastic and therefore not permanent. 

The incorporation of the new material without any increase in the overall length of the book has been achieved in part by extensive re-writing, with the compression of earlier material, and in part by restricting the scope to the physical adsorption of gases (apart from a section on mercury porosimetry). The topics of chemisorption and adsorption from solution, both of which were dealt with in some detail in the first edition, have been omitted chemisorption processes are obviously dependent on the chemical nature of the surface and therefore cannot be relied upon for the determination of the total surface area and methods based on adsorption from solution have not been developed, as was once hoped, into routine procedures for surface area determination. Likewise omitted, on grounds of... 

Usually the plaques produced by either method are coined (compressed) in those areas where subsequent welded tabs are coimected or where no active material is desired, eg, at the edges. The uncoined areas usually have a Bmnauer-Emmet-TeUer (BET) area in the range of 0.25—0.5 m /g and a pore volume >80%. The pores of the sintered plaque must be of suitable size and intercoimected. The mean pore diameter for good electrochemical efficiency is 6—12 p.m, deterrnined by the mercury-intmsion method. 

The equilibrium between a compressed gas and a liquid is outside the scope of this review, since such a system has, in general, two mixed phases and not one mixed and one pure phase. This loss of simplicity makes the statistical interpretation of the behavior of such systems very difficult. However, it is probable that liquid mercury does not dissolve appreciable amounts of propane and butane so that these systems may be treated here as equilibria between a pure condensed phase and a gaseous mixture. Jepson, Richardson, and Rowlinson39 have measured the concentration of... 

Mercury has a structure obtained by compressing the cubic close packed structure along a three-fold axis, causing the six equatorial distances (3.463 A.) to become greater than the six others (2.999 A.). The values of n are 0.11 and 0.63, respectively, leading to 72(1) = 1.440 A. The increasing weakness of the six longer bonds in the sequence zinc, cadmium, mercury is noteworthy. 

Matter occupies space, and matter is made up of atoms, so atoms occupy space. It is extremely difficult to compress a solid such as copper or a liquid such as mercury, because the electron cloud of each atom occupies some volume that no other atom is able to penetrate because of electron-electron repulsion. Example shows how to estimate the volume of an atom from the density of a sample, the molar mass of the substance, and Avogadro s number. 

Mercury fulminate is a pale brownish solid, insoluble in cold water, but dissolving slightly in hot water to a solution which does not give the normal mercury reactions. In cold conditions it is stable, but at higher temperatures gradually decomposes and loses strength as an explosive. It has a density of 4-45 g ml-1 and a velocity of detonation, when compressed to a practical density of 2-5, of about 3600 m s-1. 

A further rising of the reservoir causes a compression of the gas in the capillary C (closed). Capillary D is open and connected to the vacuum system. The difference Ah between the two mercury heights corresponds to a pressure difference Ap = pg-Ah (Ah in mm gives numerically Ap in torr) p is the density of mercury. If the compression of the gas in B and C is isothermal, we can write ... 

Measurements of particle porosity are a valuable supplement to studies of specific surface area, and such data are particularly useful in the evaluation of materials used in direct compression processes. For example, both micromeritic properties were measured for several different types of cellulosic-type excipients [53]. Surface areas by the B.E.T. method were used to evaluate all types of pore structures, while the method of mercury intrusion porosimetry used could not detect pores smaller than 10 nm. The data permitted a ready differentiation between the intraparticle pore structure of microcrystalline and agglomerated cellulose powders. 

---