Silicon dioxide powders

Sodium sulfate precipitation is not usually recommended for most murine MAbs because mouse/rat IgG can be degraded by the relatively high temperature (25°C) used during this procedure. If lipid contamination of ascitic fluids is a particular problem, add silicone dioxide powder (15 mg/mL), and centrifuge for 20 min at 2000g. Use the method described in Chapter 10, Section 3.2.1. 

Acetone-Pis an unstable, white powder or crystalline mass with a melting point of 90 to 93 Celsius. The solid is insoluble in water, but soluble in ether and tetrahydrofuran. It is quite unstable and is rarely used in military or commercial explosives. However it can be utilized as a primary explosive in blasting caps or detonators when desensitized with appropriate materials. To do so, it should be mixed with gum Arabic, carbon black, tri sodium phosphate, chalk, or silicon dioxide powder, and then mixed with a small amount of paraffin s or saturated oils prior to use. Acetone-P can also be slurried with 10% water and 5% hexane for use in blasting caps or detonators. Pure acetone-P should not be used by itself, as it will decay over time potentially leading to explosions. Acetone-P is rather volatile, and a small sample left out in the open will completely evaporate after several days—partly due to decomposition. Acetone-P can also be used in initiating compositions when mixed with sulfur nitride or other primary explosives, and then added to a small amount of a saturated oil. The sulfur nitride and other primary explosives can be replaced by bari urn chromate, copper perchlorate, or lead chromate. Even when acetone-P has been successfully desensitized, it should be used withi n 2 weeks of preparation. ... 

Violent reactions with ammonium salts, chlorate salts, beryllium fluoride, boron diiodophosphide, carbon tetrachloride + methanol, 1,1,1-trichloroethane, 1,2-dibromoethane, halogens or interhalogens (e.g., fluorine, chlorine, bromine, iodine vapor, chlorine trifluoride, iodine heptafluoride), hydrogen iodide, metal oxides + heat (e.g., beryllium oxide, cadmium oxide, copper oxide, mercury oxide, molybdenum oxide, tin oxide, zinc oxide), nitrogen (when ignited), silicon dioxide powder + heat, polytetrafluoroethylene powder + heat. 

If lipid contamination is a pardcular problem, add silicone dioxide powder (15 mg/mL) and centrifuge for 20 min at 2000g . 

Silicon, like carbon, is unaffected by dilute acids. Powdered silicon dissolves incompletely in concentrated nitric acid to give insoluble silicon dioxide, SiOj ... 

Oldhamite, see Calcium sulfide Opal, see Silicon dioxide Orpiment, see Arsenic trisulfide Oxygen powder, see Sodium peroxide... 

Ceramic materials are typically noncrystalline inorganic oxides prepared by heat-treatment of a powder and have a network structure. They include many silicate minerals, such as quartz (silicon dioxide, which has the empirical formula SiO,), and high-temperature superconductors (Box 5.2). Ceramic materials have great strength and stability, because covalent bonds must be broken to cause any deformation in the crystal. As a result, ceramic materials under physical stress tend to shatter rather than bend. Section 14.22 contains further information on the properties of ceramic materials. 

An absorbent may also be necessary when the formulation contains a hygroscopic ingredient, especially when absorption of moisture produces a cohesive powder that will not feed properly to the tablet press. In such instances, silicon dioxide has been found to be of particular value. 

Silica, or silicon dioxide, occurs in various forms including chalcedony, which is a decorative material chert, which is used in abrasives flint, which is used in abrasives and ceramics jasper, which is used for decorative purposes quartz, which is a constituent of sand tripoli, which is found in scouring powders, polishers, and fillers cristobalite, which is used in high temperature casting and specialty ceramics diatomaceous earth, which is used in filtration processes and as a filler and finally, silica gel, which is used in dehydrating and drying. Note, however, that the material of concern is silica, and not silicates, which are relatively harmless derivatives of silica, nor silicones, synthetic materials used especially as lubricants. Neither silicates nor silicones cause proliferative conditions. 

Dusting Powders are sprinkled onto the intact skin and consist of talc, magnesium stearate, silicon dioxide (silica), or starch. They adhere to the skin, forming a low-friction film that attenuates mechanical irritation. Powders exert a drying (evaporative) effect. 

Glidants (e.g., colloidal silicon dioxide, talc) may need to be added to achieve desired flow properties, especially when the drug/filler ratio is relatively high. Usually, there is an optimum concentration of glidant for best flow, often less than 1% for the colloidal silicas (14,15). The following order of effectiveness of glidants has been reported for two powder systems fine silica > magnesium stearate > purified talc (16). 

Indeed, recently SEDDS themselves have been delivered as liquids absorbed onto powders such as colloidal silicon dioxide or microcrystalline cellulose (Nazzal et al., 2002). Selection of the absorbent was obviously critical to the performance of the system but, as an aside, it seems that this approach negates the rapid release properties of a SEDDS. It will be interesting to follow the future of this technology. 

Add, in small quantities, the remaining half of magaldrate cake or powder and disperse well. Mix for 1 hour and then remove heat. (Adjust the speed of the agitator and of the homogenizer to maintain the mobility of suspension.) Separately blend silicon dioxide colloidal with xanthan gum and disperse the blend in glycerin, with constant mixing. 

PLACE SOME OF THE GEL ON A METAL JAR LID. HEAT.THE SILICIC ACID (H2SiO,) GIVES UP WATER (H20) AND TURNS INTO A GRAYISH-WHITE POWDER OF SILICON DIOXIDE (SiOz). 

In the gelled electrolyte battery, die sulfuric acid electrolyte has been immobilized by a diixolropic gel. This is made by mixing an inorganic powder such as silicon dioxide, SiCL, with the acid. Other cells use a highly absorbent separator to immobilize the electrolyte. 

Oxides of metals in Group 1 of the periodic table, such as potassium and sodium, are also highly reactive, though. It would not be safe to allow these chemicals to remain in the airbag, so the potassium and sodium oxides then react with silicon dioxide (Si02). This reaction forms an alkaline silicate powder. Alkaline silicate, a type of glass, will not burn and the resulting powder is harmless. 

As a rule, silicone liquids do not dissolve in water and in low-molecular aliphatic alcohols however, they dissolve well in many aromatic and chlorinated hydrocarbons. These liquids are not affected by diluted acids and alkali and interact only with concentrated acids and alkali. They bum much less energetically than hydrocarbon oils and most organic liquids the products of their complete combustion are carbon dioxide, water vapour and silicon dioxide (in the form of very thin powder). 

Silicon Dioxide and Silicic Acid, (a) Wet a little silicon dioxide (very finely powdered quartz, or better the product of Preparation 41), test with litmus, and note that litmus is not... 

Collect a little of a mixture of anhydrous potassium carbonate and sodium carbonate (the mixture melts more easily than either salt alone) in a loop on the end of a platinum wire and melt it in the Bunsen flame to a clear bead. Dip the bead into powdered silicon dioxide and melt it again. Note that the liquid bead effervesces until the silica has dissolved. 

Magnesium carbonate V Manganese carbonate P. 70 Manganese dioxide, powder IV, XI Nickel carbonate XI Phosphorus, red II, X Porcelain chips, unglazed E. 5, P. 56 Potassium carbonate IX Potassium chlorate III, VIII Potassium dichromate IV Potassium hydroxide II, III Potassium iodate VIII Potassium iodide IV, VIII Potassium nitrate IV, XI Potassium permanganate IV, VIII Potassium sulphate Q. 3 Silicon dioxide, precipitated IX Silicon dioxide, coarse sand P. 66, 67 Silicon dioxide, fine sand P. 8, 43 Sodium bicarbonate P. 55 Sodium bromide IV Sodium carbonate, anhydrous III, IX, XI... 

Magnesium Silicate occurs as a very fine, white powder free from grittiness. It is a synthetic, usually amorphous form of magnesium silicate in which the molar ratio of magnesium oxide (MgO) to silicon dioxide (Si02) is approximately 2 5. It is insoluble in water and in alcohol, but is readily decomposed by mineral acids. The pH of a 1 10 slurry is between 7.0 and 10.8. 

Fumed silica occurs as a white, fluffy, nongritty powder of extremely fine particle size and is hygroscopic. The wet-process silicas occur as white, fluffy powders or as white, microcellular beads or granules and are hygroscopic or absorb moisture from the air in varying amounts. All of these forms of Silicon Dioxide are insoluble in water and in organic solvents, but they are soluble in hydrofluoric acid and in hot, concentrated solutions of alkalies. 

If a powder flows poorly, the vibrator can be used, but it also causes powder segregation and stratification. The addition of glidant (occasionally lubricant) in the powder mixtures can readily increase flowability at the low concerntration. Talc or fumed silicon dioxide is an example of a glidant. If this is not sufficient to improve the flow, other means of flow improvement are necessary. There are two main factors that affect powder flow particle size and particle shape. The more spherical a particle is, the better it flows. Small particles are very cohesive and hence do not flow well, but increasing the particle size will improve flow. With the aid of spray drying or spheronizers, particles become spherical. 

Note The remainder of the composit consisted of 80 wt% filler consisting of barium- aluminum-boron silicate glass powder, silicon dioxide-zirconium dioxide, and ytterbium fluoride. For dental composites lower viscosities are preferred because of their flowability. 

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