Silica applications

Astrakanite, 5 785t 22 846, 863 Astringents, 7 847-848 Astronomy, vitreous silica applications in, 22 443-444... 

Determination of Silica (Applicable to Grade ll IV onlyJ. To the ash in the platinum crucible, add 5 ml of HC1 and a few drops of sulfuric acid. Evaporate and ignite. Cool in a desiccator and weigh. Calculate the loss in weight as percent silica as follows, and retain the residue for grit detn ... 

Due to the variety in porous structure, particle size and surface area, pure silica gels and powders find a very wide range of applications. Variation in preparation methods and parameters allows the tailoring of the substrate properties for specific application needs. The main features in the silica applications are its porosity, active surface, hardness, particle size and the viscous and thixotropic properties. Although most applications are based on a combination of those, a classification according to the main properties of interest may be set up. For references, the reader is referred to the works of Iler6 and Unger7 and to the references cited in chapter 8. 

Tribble J. S., Arvidson R. S., Lane M., Ill, and Mackenzie F. T. (1995) Crystal chemistry, and thermodynamic and kinetic properties of calcite, dolomite, apatite, and biogenic silica applications to petrologic problems. Sedim. Geol. 95, 11-37. 

N. Mimura, S. Tsubota, K. Murata, K. K. Bando, J. J. Bravo-Suarez, M. Haruta, S. T. Oyama, Gas-phase radical generation by Ti oxide clusters supported on silica Application to the direct epoxidation of propylene to propylene oxide using molecular oxygen as an oxidant, Catal. Lett. 110 (2006) 47. 

Griessbach (17) showed that five companies produced silica sols in 1933. Most products were very dilute, and only one could be considered concentrated. The most concentrated sol available at that time was a product called Kieselsol I.G. (made by I.G. Farbenindustries), which contained 10% silica and was stabilized with ammonium hydroxide. The characteristics of most of the sols were undetermined. Moreover, the difficulty of making a reproducible product that would perform in a predictable manner for specific uses was technically impossible at that time. This difficulty, most likely, was the major reason that colloidal silica applications did not increase rapidly. Iler (18) pointed out that colloidal silica was not accepted for wide commercial use until methods were discovered for producing sols with high concentrations that would not gel or settle with time. The first steps to achieving that goal occurred in 1941 (discussed in the preceding section on preparation procedures). 

Aerosilogel, definition, 7 Aerosol, definition, 7 After-treated synthetic amorphous silicas applications, 490 example, 489/... 

Both silica gels and precipitates are found as abrasives (as well as thickeners) in toothpaste. Silicas are especially useful in the production of clear gel-type toothpastes, because it is possible to match the index of refraction of the liquid components of the formulation to that of the silica to provide the desired level of abrasivity while retaining the transparency of the toothpaste. This cannot be done with conventional abrasive agents, such as calcium carbonate. The concept of combining an abrasive silica with a thickening silica has become the basis for many standard formulations and now represents one of the high-volume silica applications. This combination allows the formulator to independently adjust abrasivity level, cleaning power, and viscosity. 

E.H. Oliw, Chromatography of B Prostaglandins on P-Cyclodextrin Silica Application to Analysis of Major E Prostaglandins in Human Seminal Fluid, J. Chromatogr., 421(1987)117. 

Chanthateyanonth, R. and Alper, H. (2003) The first s5mthesis of stable paUadium(II) PCP-type catalysts supported on silica - application to the Heck reaction. J. Mol. Cat. A Chem., 201, 23-31. 

Karimi, B. and Enders, D. (2006) New IV-heterocyclic carbene palladium complex/ionic liquid matrix immobilized on silica application as recoverable catalyst for the Heck reaction. Org. Lett., 8, 1237-40. 

Hagiwara, H., Sugawara, Y, Isobe, K. et al. (2004) Immobilization of Pd(OAc)2 in ionic liquid on silica application to sustainable Mizoroki-Heck reaction. Org. Lett., 6, 2325-8. 

O Leary, R, Krosveld, N. R, De Jong, K. R, van Koten, G., and Klein Gebbink, R. J. M. 2004. Facile and rapid immobilization of copper(II) bis(oxazoline) catalysts on silica Application to Diels-Alder reactions, recycling, and unexpected effects on enantiose-lectivity. Tetrahedron Lett. 45(16) 3177-3180. 

Wang L, Reis A, Seifert A, Philippi T, Ernst S, Jia M, Thiel WR (2009) A simple procedure for the covalent grafting of triphenylphosphine ligands on silica application in the palladium catalyzed Suzuki reaction. Dalton Trans 17 3315-3320... 

Giraldo LF, Lopez BL, Perez L, Urrego S, Sierra L, Mesa M (2007) Mesoporous silica applications. Macromol Symp 258 129-141... 

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