Sulfate bulk barium

It was pointed out in Section XIII-4A that if the contact angle between a solid particle and two liquid phases is finite, a stable position for the particle is at the liquid-liquid interface. Coalescence is inhibited because it takes work to displace the particle from the interface. In addition, one can account for the type of emulsion that is formed, 0/W or W/O, simply in terms of the contact angle value. As illustrated in Fig. XIV-7, the bulk of the particle will lie in that liquid that most nearly wets it, and by what seems to be a correct application of the early oriented wedge" principle (see Ref. 48), this liquid should then constitute the outer phase. Furthermore, the action of surfactants should be predictable in terms of their effect on the contact angle. This was, indeed, found to be the case in a study by Schulman and Leja [49] on the stabilization of emulsions by barium sulfate. 

Because the regions of the alimentary tract vary widely ia pH and chemical composition, many different commercial formulations of barium sulfate are available. The final preparations of varyiag viscosity, density, and formulation stabiUty levels are controlled by the different size, shape, uniformity and concentration of barium sulfate particles and the presence of additives. The most important additives are suspending and dispersiag agents used to maintain the suspension stabiUty. Commercial preparations of barium sulfate iaclude bulk and unit-dose powders and suspensions and principal manufacturers are E-Z-EM (Westbury, New York), Lafayette-Pharmacol, Inc. (Lafayette, Indiana), and Picker International, Inc. (Cleveland, Ohio). 

The rate of aging is strongly influenced by other solutes in solution and thus can be increased or decreased by the presence of excess lattice ions in solution. Barium sulfate ages more slowly in barium ion solution than in sulfate and more slowly in sulfate than in water. The aging of silver chloride is impeded by silver ion, but speeded by chloride ion a similar effect exists for silver bromide. For lead chromate no particular lattice ion effect was noticed. Apparently the rate of aging does not parallel solubility, which is decreased by the common ion effect. Kolthoff and others postulated that the solubility in the adsorbed water layer may be different from that in the bulk of the solution. For example, in the case of silver chloride in the presence of adsorbed chloride ion, the solubility may be increased owing to the formation (Section 7-7) of AgCl2 in the immediate vicinity of the surface. It appears likely that the adsorbed lattice ion also has a pronounced effect on the rate of recrystallization, which is not necessarily parallel with solubility even in the adsorbed water layer. 

Inexpensive, finely ground minerals like barium sulfate (barytes), dolomite, limestone (whiting), clays, and silica are widely used to provide bulk and reduce the cost of friction material formulations. These materials also act as friction modifiers and alter the performance of the end product. Other less commonly used fillers are hollow and solid organic and inorganic microspheres and fly ash. 

Filler Opacify compound, increase hardness, reduce cost Changes refractive index and reflective properties, adds bulk to compound Calcium carbonate, magnesium carbonate, barium sulfate, carbon or glass fibres... 

The deactivation of these catalysts is probably due to the formation of highly stable species, such as barium sulfate. In addition to the possible encapsulation of Pd particles, the migration of barium from the bulk to the surface of the support is probably responsible for the lower activity in methane oxidation. The possible formation of barium or lanthanum sulfate covering Pd particles will be further investigated. 

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