Silica, amorphous-diatomaceous earth

Silica, amorphous—diatomaceous earth 625 Titanium dioxide 679... 

Chlorinated diphenyl oxide, 137 Hexabromobiphenyl, 591 Octabromobiphenyl, 591 Hydrogenated terphenyl, 386 Fpoxy Resins, 298 Portland cement, 594 Fuel oil 2, 352 Fuel oil 4, 352 Fuel oil 2-D, 352 Silica, amorphous-diatomaceous earth, 625... 

INFUSORIAL EARTH KIESELGUHR SILICA, AMORPHOUS-DIATOMACEOUS EARTH (UNCALCINED) (ACGIH)... 

Silica, amorphous, diatomaceous earth, containing less than 1% crystalline silica... 

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. 

A crystalline form of free silica, extremely hard and inert chemically very resistant to heat. Quartz in refractory bricks and amorphous silica in diatomaceous earth are altered to cristobalite when exposed to high temperatures (calcined). Cristobalite is extensively used in precision casting by the hot wax process, dental laboratory work, and certain speciality ceramics. 

Amorphous free silica (Noncrystalline) Diatomaceous earth... 

Amorphous free silica (Noncrystalline) Diatomaceous earth A soft, gritty amorphous silica composed of minute siliceous skeletons of small aquatic plants. Used in filtration and decoloration of liquids, insulation, filler in dynamite, wax, textiles, plastics, paint, and rubber. Calcined and flux-calcined diatomaceous earth contains appreciable amounts of cristobalite, and dust levels should be the same as for cristobalite. 

The 2003 ACGIH proposed threshold limit value-time-weighted average (TLV-TWA) for amorphous silica, natural diatomaceous earth, is lOmg/m for the inhalable particulate and 3mg/m for respirable dust containing no asbestos and <1% quartz. 

Amorphous silica. See Diatomaceous earth, amorphous Silica, amorphous hyif rated... 

Amonyl BR1244. See Lauralkonium bromide Amonyl DM. See Quaternium-82 Amorphous phosphorus. See Phosphorus, red Amorphous silica. See Silica, fused Diatomaceous earth, amorphous Silica, amorphous hydrated... 

Indutabs. See Calcium hypochlorite Infusorial earth. See Diatomaceous earth, amorphous Diatomaceous earth Inhibisll . See Silica, amorphous Inipol 002. See Oleyl propylene diamine dioleate... 

Amorphous silica lacks a definite shape and an orderly atomic latticework. Types of amorphous silica include glass, vitreous glass fiber, large flocculated silica gel, diatomaceous earth, and opaline phase-fused silica in granular and powder form. These products provide high purity, reinforcement, great surface area, flatting properties, and thixotropy. Fused silica has an extremely low coefficient of linear thermal expansion and has become quite popular, especially in electronics applications. The amorphous silicas are compatible with thermosets, thermoplastics, silicone rubber, and other elastomers. 

MicrocrystaUine Silicas. Various microcrystalline (cryptocrystalline) materials such as flint, chert, and diatomaceous earth are found ia nature (see Diatomite). These may arise from amorphous silica, often of biogenic origin, which undergoes compaction and microcrysta11i2ation over geologic time. 

Diatomaceous earth A soft, gritty amorphous silica composed of minute siliceous skeletons of small aquatic... 

In addition to the above crystalline phases sdica also exists in a few micro-crystadine forms. Such micro crystalline or cryptocrystalline silicas occur in nature and include diatomaceous earth, flint, and chert. They are mostly of biogenic origin forming from compaction of amorphous silica over geologic time. 

Approximately 40% of synthetic amorphous silica production is in Europe, followed by North America at 30%, and Japan at 12%. Although deposits of naturally occurring amorphous silicas are found in all areas of the wodd, the most significant commercial exploitation is of diatomaceous earth in industrialized countries (see Diatomite). This is because of the high cost of transportation relative to the cost of the material. Woddwide manufacturers of amorphous silica products are listed in Table 2. 

Diatomite. also known as diatomaceous earth, or kieselgubr, consists mainly of accumulated shells or frustules of intricately structured amorphous hydrous silica secreted by diatoms, which are microscopic, onc-celled golden brown algae of the class Bacillariophyceae. Diatoms exist in many different environments and arc abundant in regions of oceanic upwelling. 

This is naturally occurring amorphous silicic acid from the skeletons of diatoms and hence is often referred to as diatomaceous earth. It has less adsorptive properties than silica. 

---