Barium sulfate particles

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). 

Takahashi S, Patrick G. 1987. Long-term retention of Ba in the rat trachea following local administration as barium sulfate particles. Radiat Res 110 321-328. 

The particle size of barium sulfate may vary from a fraction of a micron to several microns or more (48). Ultrafine grain size by itself may give inferior visualization of the gastric mucosa but the particles can be more easily held in suspension. On the other hand, particles larger than 1 jam may offer better contrast, provided that they can be made to stay in suspension. An electron micrograph of barium sulfate particles of less than 1 jam in diameter shows that they are of irregular shape (53). The influence of microcrystalline shape on the coating property of the suspension is not well studied. 

Pozamsky, G. and Matijevic, E.. Particle adhesion in model systems 16 Barium sulfate particles on glass and protein surfaces. J. Adhesion. 63. 53. 1997. 

Some algae (e.g., Chara, Closterium moni-liferum, Closterium tumidulum) accumulate barium as barium sulfate particles for orientation purposes in gravitational fields (Sie-vers and Schrbter 1971, Schrbter etal. 

Gillani R, Ercan B, Qiao A, Webster TJ. Nanofunctionalized zirconia and barium sulfate particles as bone cement additives, hit J Nanomed 2010 5 1-11. 

Some ionic adsorbents show unusu ll properties (see, for example, [15, 58, 68-70]). Belyakova and co-workers [68-70] have proposed barium sulfate as a selective adsorbent They successfully used barium sulfate modified with sodium chloride for separation of some isomers of unsaturated, aromatic hydrocarbons, and oxygen- and nitrogen-containing heterocyclic compounds [68]. Barium sulfate was prepared by interaction of s< ium sulfate and barium chloride solutions of various concentration present in equimolar proportions. The specific surface areas varied from 2.5 to 8 m /g. To investigate this ionic adsorbent, glass Ccipillary columns (1 mm i.d.) were packed with barium sulfate particles (0.16-0.20 mm). The maximum value of separation selectivity for all xylene isomers was observed on barium sulfate samples modified with 15% sodium chloride solution [69]. According to electron spectroscopy for chemical analysis these samples contained on the surface about 2% of... 

In general, partiele uptake is a fairly rapid process, but again, there are site-to-site differenees in the speed at which uptake oecurs. Stirling and Patrick (63), using intratracheal instillation, noted that no instilled barium sulfate particles... 

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. 

Barium metal and most barium compounds are highly poisonous. A notable exception is barium sulfate which is nontoxic because of its extreme iasolubihty ia water. Barium ion acts as a muscle stimulant and can cause death through ventricular fibrillation of the heart. Therefore, care must be taken to avoid contact with open areas of the skin. Workers must wear respirators (of type approved for toxic airborne particles), goggles, gloves, and protective clothing at all times. The toxic barium aluminate residue obtained from barium production is detoxified by reaction with a solution of ferrous sulfate and converted iato nontoxic barium sulfate. According to OSHA standards, the TWA value for Ba and Ba compounds ia air is 0.5 mg/m. ... 

Scratch resistance depends on the hardness of the added particles. The problem of a lack of this property can be addressed by adding chemically identical particles of different crystal modification and Mohs hardness. The preferred additives are silica, alumina, layered silicates such as kaolin, titania, barium sulfate and calcium carbonate. The latter is only suitable for the DMT process owing to side reaction caused by acidity during the terephthalic acid (TPA) route. 

Gross alpha and gross beta activity can be determined by various radioactive counters, such as internal proportional, alpha scintillation, and Geiger counters. Radium in water can be measured by co-precipitating with barium sulfate followed by counting alpha particles. Radium-226 can be measured from alpha counting of radon-222. Various methods are well documented (APHA, AWWA, and WEF 1998. Standard Methods for the Examination of Water and Wastewater, 20 ed. Washington DC American Public Health Association). 

The refined source profiles that best reproduced the coarse fraction are listed in table 7. The calculated profiles of the two crustal components follow those of Mason ( ), though the calcium concentration of 20 in the limestone factor is less than the reported value. The paint pigment profile strongly resembles that calculated for the fine-fraction data. The only major difference is that unlike the fine fraction, the coarse-fraction profile does not associate barium with the paint-pigment factor. The calculated sulfur concentration in the coarse-fraction sulfate factor is much less than that in the fine-fraction and there are sizable concentrations of elements such as aluminum, iron, and lead not found in the fine-fraction profile. The origin of this factor is not clear although as described earlier a possible explanation is that a small part of the sulfate particles in the fine fraction ended up in the coarse samples. 

Takiyama (6) prepared highly monodispersed spindle-type particles of barium sulfate (BaS04) by decomposing the Ba-EDTA complex with hydrogen peroxide. In this reaction, the initial concentration of the Ba-EDTA complex is a decisive factor in separation of nucleation and growth stages. 

Several studies have considered the influence of filler type, size, concentration and geometry on shear yielding in highly loaded polymer melts. For example, the dynamic viscosity of polyethylene containing glass spheres, barium sulfate and calcium carbonate of various particle sizes was reported by Kambe and Takano [46]. Viscosity at very low frequencies was found to be sensitive to the network structure formed by the particles, and increased with filler concentration and decreasing particle size. However, the effects observed were dependent on the nature of the filler and its interaction with the polymer melt. 

Fig. 27. The relationship between particle size and decomposition rate of barium sulfate on the NSR catalyst.

Supplementary components include 10-60% of calcium carbonate with an average particle size of 1-20 p and barium sulfate. 

Figure 7. Scattering of white pigments as a function of particle size (A = 550 nm) a) Rutile b) Anatase c) Zinc sulfide d) Zinc oxide e) White lead f) Barium sulfate...

The refractive index n of ZnS, which determines its scattering properties, is 2.37 and is much greater than that of plastics and binders (n = 1.5-1.6). Spheroidal ZnS particles have their maximum scattering power at a diameter of 294 nm. Barium sulfate does not directly contribute to the light scattering due to its relatively low refractive index (n = 1.64), but acts as an extender, and increases the scattering efficiency of the ZnS. 

Figure 21. Scanning electron micrograph of lithopone. The larger particles are barium sulfate (mean size 1.0 pm) and the smaller particles are zinc sulfide (mean size 0.3 pm).

Both zinc sulfide and barium sulfate are insoluble in water. To improve the stability of lithopone, a small amount of a cobalt salt is added to the precipitated mixture. The mixture has to be filtered off, dried, and calcined. The calcination is carried out in rotary calciners at temperatures between 600 and 700°C. During calcination, the particle size of zinc sulfide grows from its original size (about 0.1 Jim) to the pigmentary optimal size of 0.4—0.6 Jim. 

PRECIPITATE. i, ppt). Small particles that have settled out of a liquid or gaseous suspension by gravity, or that result from a chemical reaction. Precipitated compounds, such as blanc fixe (barium sulfate, are... 

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