Silica, amorphous-fume

ACGIH Silica, amorphous—fume. Documentation of the Threshold Limit Values atid Biological Exposure Indices, 7th ed, p 4. Cincinnati, OH, American Conference of Governmental Industrial Hygienists, 2001... 

A review of chemical databases reveals that different CASRN have been assigned to the different physical forms of Si02- The assignment of these CASRN was unrelated to TSCA. The EPA has taken the position that, for TSCA purposes, the different physical forms of Si02 are considered to be included under the TSCA Inventory listing for silica, CASRN 7631-86-9. For example, the EPA instructs the regulated community to treat silica, amorphous, fumed, crystalline-free (CASRN 112945-52-5), and silica gel, precipitated, crystalline-free CASRN (112926-00-8), as silica (CASRN 7631-86-9) for TSCA Inventory purposes. 

Silica, amorphous, fumed, crystalline free 112945- 52-5 No Yes No For TSCA Inventory Purposes use 7631-86-9... 

CAS 112945-52-5 EINECS/ELINCS 231-545-4 Synonyms Amorphous silica dust Cl 77711 Colloidal silica Colloidal silicon dioxide Eossil flour Eumed silica Fumed silicon dioxide Pigment white 27 Silica, amorphous Silica, amorphous fumed Silica, pyrogenic Silicic anhydride Silicon dioxide Definition High surface area aggregate particles of silica, with min. 89.5% SiOj content Empirical OjSi Formula SiOj... 

Silica, amorphous Silica, amorphous fumed. See Silica, fumed... 

Precipitated amorphous hydrated silica and fumed anhydrous silica, inorganic reinforcing agent. 

Fumed silica - [SILICA - AMORPHOUS SILICA] (Vol 21) - [SILICONCOMPOUNDS-SILANES] (Vol 22) -silicon tetrachloride m prdn of [SILICON COMPOUNDS - SILICON HALIDES] (Vol 22)... 

There are a variety of other silicas. These include the metastable silica-W, which has a very low density (1.97 gcm ), and whose structure consists of edge-sharing chains of Si04 tetrahedra, the microcrystaUine diatomaceous earths, various forms of noncry stalline silica inclnding vitreous silica (glassy silica), and the finely divided amorphous silicas such as dry silica gel, fumed silicas, and colloidal silicas. 

Perspectives. Ordered mesostnictured and mesoporous silica has been known for little more than ten years. Tremendous progress has been made with respect to precise control of the structure, texture, and chemical fimctionality of the surface of these materials. His lecture surveyed the synthesis of such materials, with a focus on organically ordered mesoporous materials. Quite a number of contributions dealt with amorphous fumed silica, its Physical-Chemical Features and Related Hazard Risk Assessment (M. Heinemann), the description of fractal aggregates (C. Batz-Sohn), and the Characterization of Size and Structure of Fumed Silica Particles in Suspension (F. Babick). E. Brendle reported on Adsorption of Water on Fumed Silica, and in a second paper he summarized research on Methylene Chloride Adsorption on Pyrogenic Silica Surfaces. 

The cata ts used in this work were prepared by ion exchange of the PtfNHj) cations formed in an aqueous Pt(NH3)4(N03)2 solution with a high-suiface-area Cab-O- HS-S amorphous fumed silica (300 m /g BET surface area). Following ion exchange, the catalysts... 

Various industries use large quantities of fumed and precipitated silica (amorphous silica). These forms of silica do not cause silicosis but protection from exposure to dust must be provided because any excessive dust decreases efficiency of lungs. ... 

Silica, amorphous (diatomaceous earth, precipitated and gel silica) Possesses little or no potential to oause silicosis. Most sources of amorphous silica contain quartz (see orystalline silica, below). If greater than 1% quartz is present, the quartz hazard must be addressed. When strongly heated (calcined) with limestone, diatomaceous earth becomes crystalline and can cause silicosis. Amorphous silica has been associated with lung fibrosis, but the role of crystalline silica contamination remains controversial. 10 mg/m (precipitated silica, diatomaceous earth, silica gel) 3 mg/m (respirable dusH 2 mg/m (silica fume) 3000 mg/m White to gray powders. Odorless with a negligible vapor pressure. The TLV for dusts is 10 mg/m if no asbestos and less than 1% quartz ate present. 

Amorphous fumed silica promotes several Diels-Alder reactions in gaseous CO2 and scC02. For the reaction of methyl vinyl ketone and penta-1,3-diene at 80 C, the yield decreases as the CO2 pressure increases because the concentration of the reactant adsorbed on the silica surface decreases. 

Legrand and co-workers [8] and the important NMR work by Brinker and co-workers on the formation of silica in the sol-gel process [9]. We assume that much of this is covered elsewhere in this volume. In addition, the huge subject of template-synthesized mesoporous silicas, for which there is a very large recent NMR literature, is omitted from this paper, which focuses on what is commonly referred to as amorphous silica, e.g., silica gels, precipitated silicas and fumed silicas. 

In The Chemistry of Silica [1], Her used the term silica powders as a broad category encompassing silica gels, precipitated silicas, and fumed or pyrogenic silicas. These are all forms of synthetic amorphous silicon dioxide, a broad category that also includes another form — silica sols or coUoidal silica — that is not a powder, but rather a dispersion of discrete silica particles in a liquid medium. 

Toxicology LD50 (oral, rat) > 2000 mg/kg Aerosil R972 [Degussa/Aerosil Silanes Degussa AG/Aerosil Silanes] Chem. Descrip. Syn. amorphous fumed silica Chem. Analysis SiOj (> 99.8%), ALO, (< 0.05%), TiOj (< 0.03%)... 

Amorphous silica dust See Silica, fumed Amorphous silica gel. See Silica, amorphous AMP. SeeAminomethyl propanol... 

Aluminum hydroxide Aluminum silicate, Boron carbide Carbon black Carbon fiber, Cellulose, Feldspar Graphite LX-782 Poly/inyl chloride Slllce Silica, amorphous hydrated. Silica, fumed,... 

Propiolactone Propyl alcohol Propylene carbonate Propylene glycol cocoate Propylene glycol laurate adhesive, food packaging Propylene glycol stearate Rapeseed (Brassica campestris) oil Rice (Oryza sativa) bran oil Rice (Oryza sativa) starch Rosin Rosin, polymerized Safflower (Carthamus tinctorius) oil Sandarac (Callitris quadrivalvis) gum Sebacic acid Sesame (Sesamum indicum) oil Shark liver oil Shellac Silica Silica, amorphous Silica, fumed Silica, hydrated Silicone emulsion Sodium alum Sodium bisulfate Sodium borate Sodium borate decahydrate Sodium chlorate Sodium chlorite Sodium chromate Sodium cocoate... 

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