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Amorphous silica(CAS No. 7631-86-9)

Amorphous silica SiO2 (cas 7631-86-9) Molecular Structure

7631-86-9 Structure

Identification and Related Records

【Name】
Amorphous silica
【CAS Registry number】
7631-86-9
【Synonyms】
Silica Dioxide
Diatomaceous earth
Silicic anhydride
【EINECS(EC#)】
231-545-4
【Molecular Formula】
SiO2 (Products with the same molecular formula)
【Molecular Weight】
60.08
【Inchi】
InChI=1/O2Si/c1-3-2
【InChIKey】
VYPSYNLAJGMNEJ-UHFFFAOYSA-N
【Canonical SMILES】
O=[Si]=O
【MOL File】
7631-86-9.mol

Chemical and Physical Properties

【Appearance】
white crystals or powder
【Density】
2.6
【Melting Point】
1610℃
【Boiling Point】
>100?°C(lit.)
【Refractive Index】
1.46
【Flash Point】
n/a
【Water】
insoluble
【Solubilities】
insoluble
【Color/Form】
Amorphous powder
Transparent to gray powder (Note: Amorphous silica is the non-crystalline form of O2Si). ... solid
Silica gel is a coherent, rigid, continuous three-dimensional network of spherical particles of colloidal microporous silica.
【Stability】
Stable.
【HS Code】
28112200
【Storage temp】
Refrigerator (+4°C)
【Computed Properties】
Molecular Weight:60.0843 [g/mol]
Molecular Formula:O2Si
H-Bond Donor:0
H-Bond Acceptor:2
Rotatable Bond Count:0
Exact Mass:59.966756
MonoIsotopic Mass:59.966756
Topological Polar Surface Area:34.1
Heavy Atom Count:3
Formal Charge:0
Complexity:18.3
Isotope Atom Count:0
Defined Atom Stereocenter Count:0
Undefined Atom Stereocenter Count:0
Defined Bond Stereocenter Count:0
Undefined Bond Stereocenter Count:0
Covalently-Bonded Unit Count:1
Effective Rotor Count:0
Conformer Sampling RMSD:0.4
CID Conformer Count:1

Safety and Handling

【Hazard Codes】
Xi:Irritant
【Risk Statements】
R36/37
【Safety Statements 】
S26;S37/39
【Skin, Eye, and Respiratory Irritations】
Irritating to the eye.
【Transport】
无资料?
【Formulations/Preparations】
USEPA/OPP Pesticide Code 072605; 46 Active Products contain amorphous silicon dioxide, celite, diatomaceous earth, or silicon dioxide. Many of these products contain other additional active pesticide ingredients. Trade Names: Chemsico Insecticide DE; Crop Guard; Diafil 610; Diasource Diatomaceous Earth Crawling Insect Killer; Diasource Diatomaceous Earth Grain Storage Insecticide; Diatect D-20; Diatect Insecticide V; Diatect Multipurpose Insecticide; Diatect Multipurpose Insecticide II; Diatect Pet Powder; Diatom Dust Insect Powder; Diatomic Earth; Dry Pyrocide Insecticide; Dryacide; Eaton's Answer II; Eaton's K.I.O. (Kills Insects Only) System; Enforcer Insecticide Powder; Flea Away; Flea Scare; Garden-Ville Diatomaceous Earth; Grapple Flea Powder; Harper Valley Diatomaceous Earth; Hi-Yield Crawling Insect Control; Insecolo; Insect Dust; Insect-Aside P.P.D. Multipurpose Insecticide; Insectaside D. E.; Insectigone; Insecto; Melocide DE-200; Melocide DE-100; Organic Resources Multipurpose Insecticide; Perma Guard Garden and Plant Insecticide D-21; Perma-Guard Commercial Insecticide D-20; Perma-Guard Grain or Seed Storage Insecticide D-10; Perma-Guard Household Insecticide D-20; Perma-Guard Kleen Bin D-20; Perma-Guard Pet and Animal Insecticide D-20; Powdered Insecticide; Protect-It; Pyrocide Insecticide II; Shellshock Insecticide; Southwest Select Diatomaceous Earth; Speer Dry Insecticide; The Graden Guy Diatomaceous Earth; Whitmire PT-239 Tri-Die Insecticide
PERMA-GUARD GRAIN OR SEED STORAGE INSECTICIDE DUST D-10--80% ACTIVE INGREDIENT.
Wettable powder
Wessalon /is/ spray-dried precipitated silica; 98-99.5% silicon dioxide, amorphous; particle sizes 1-100 microns. Other name: Sipernat.
/Cab-O-Sil* is/ 99.8% Silicon dioxide, amorphous. /A/ white powder, ultrafine particle size (.014 microns). Other names: Colloidal Silicon Dioxide, Amorphous Silica. Water dispersible. Combinations: Synergistic effect with other thickeners.
Technical grade, FCC grade, FDA grade, high-purity, 0.03 micron grade, ground and whole grain sand grades, powder, pellets, fumed silica (hydrophobic), aqueous slurries of colloidal fumed silica, ground silica, silica flour, silica gel. A range of grades and mesh sizes.
Diatomaceous earth ... (88% silica) composed of skeletons of small prehistoric aquatic plants related to algae (diatoms).
【Exposure Standards and Regulations】
The food additive silicon dioxide may be safely used in food in accordance with /specified/ conditions.
Silicon dioxide may be safely used as a component of articles intended for use in packaging, transporting, or holding food in accordance with prescribed conditions.
The food additive silicon dioxide may be safely used in animal feed in accordance with /specified/ conditions.
【Reactivities and Incompatibilities】
Fluoride, oxygen difluoride, chlorine trifluoride.
Vinyl acetate vapor may react vigorously in contact with silica gel... . /Silica gel/
【Other Preventative Measures】
Wetting processes to control dusts must be used wherever feasible. Dust-producing operations should be segregated.
SRP: The scientific literature for the use of contact lenses in industry is conflicting. The benefit or detrimental effects of wearing contact lenses depend not only upon the substance, but also on factors including the form of the substance, characteristics and duration of the exposure, the uses of other eye protection equipment, and the hygiene of the lenses. However, there may be individual substances whose irritating or corrosive properties are such that the wearing of contact lenses would be harmful to the eye. In those specific cases, contact lenses should not be worn. In any event, the usual eye protection equipment should be worn even when contact lenses are in place.
【Protective Equipment and Clothing】
FREQUENT QUANT DUST COUNTS & ANALYSES MUST BE MADE ... PARTICLE COUNTS MUST BE KEPT WITHIN SAFE LIMITS. WORKERS EXPOSED ... SHOULD HAVE YEARLY CHEST EXAM. AIRLINE FACE MASKS & PROTECTIVE SUITS MUST BE WORN IN SITUATIONS WHERE DUST CANNOT BE CONTROLLED ... .
Respirator Recommendations: Up to 30 mg/cu m: (Assigned protection factor = 5) Any dust and mist respirator.
Respirator Recommendations: Up to 60 mg/cu m: (Assigned protection factor = 10) Any dust and mist respirator except single-use and quarter-mask respirators/(Assigned protection factor = 10) Any supplied-air respirator
Respirator Recommendations: Up to 150 mg/cu m: (Assigned protection factor = 25) Any supplied-air respirator operated in a continuous-flow mode/(Assigned protection factor = 25) Any powered, air-purifying respirator with a dust and mist filter.
Respirator Recommendations: Up to 300 mg/cu m: (Assigned protection factor = 50) Any air-purifying, full-facepiece respirator with a high-efficiency particulate filter/(Assigned protection factor = 50) Any supplied-air respirator that has a tight-fitting facepiece and is operated in a continuous-flow mode/(Assigned protection factor = 50) Any powered, air-purifying respirator with a tight-fitting facepiece and a high-efficiency particulate filter/(Assigned protection factor = 50) Any self-contained breathing apparatus with a full facepiece/(Assigned protection factor = 50) Any supplied-air respirator with a full facepiece.
Respirator Recommendations: Up to 3000 mg/cu m: (Assigned protection factor = 1000) Any supplied-air respirator operated in a pressure-demand or other positive-pressure mode.
Respirator Recommendations: Emergency or planned entry into unknown concentrations or IDLH conditions: (Assigned protection factor = 10,000) Any self-contained breathing apparatus that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode/(Assigned protection factor = 10,000) Any supplied-air respirator that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode in combination with an auxiliary self-contained positive-pressure breathing apparatus .
Respirator Recommendations: Escape: (Assigned protection factor = 50) Any air-purifying, full-facepiece respirator with a high-efficiency particulate filter/Any appropriate escape-type, self-contained breathing apparatus.
【Disposal Methods】
SRP: The most favorable course of action is to use an alternative chemical product with less inherent propensity for occupational exposure or environmental contamination. Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in soil or water; effects on animal, aquatic, and plant life; and conformance with environmental and public health regulations.

Use and Manufacturing

【Use and Manufacturing】
Methods of Manufacturing

/The wet/ process is based mainly on the precipitation of amorphous silicon dioxide particles from aqueous alkali metal silicate solution by acid neutralization. Usually, sulfuric acid is used, although carbon dioxide and hydrochloric acid can be used. Depending on the final pH of the solution, t he following two different classes of synthetic amorphous silicas can be obtained: precipitated silicas - obtained in neutral or alkaline conditions; silica gels - obtained under acidic conditions. The main manufacturing steps include precipitation, filtration, washing, drying and grinding.
The manufacturing process for pyrogenic silicas is based mainly on the combustion of volatile silanes, especially silicon tetrachloride, in an oxygen-hydrogen burner. Primary particles (7-50 nm particle size) of amorphous silica fuse together in the high-temperature flame to yield stable aggregates of between 100 and 500 nm in diameter. These aggregates form micron-sized agglomerates. The finely divided silica is separated from the hydrochloric acid-containing off-gas stream in filter stations. The hydrochloric acid content of the product is commonly reduced to less than 100 ppm by desorbing the hydrochloric acid with air in a fluid-bed reactor. Pyrogenic silica appears as a fluffy white powder.
All forms of synthetic amorphous silicas can be surface-modified either physically or chemically. Methods for chemical modification of the silica particle surface (e.g. silylation) are many and various. Most common treating agents are organosilicon compounds.
DIATOMITE: FROM OPEN PIT MINING; SILICA GEL-REACTION OF SODIUM SILICATE & A MINERAL ACID; SILICA AEROGEL: TREATMENT OF A WET HYDROGEL WITH A WATER-MISCIBLE ORGANIC LIQUID; COLLOIDAL SILICA: PEPTIZATION OF SILICA HYDROGEL OR BY DESTABILIZATION OF ALKALI SILICATES.
Diatomite is mined almost exclusively by opencast methods, using bulldozers and other similar equipment to remove the material. Some diatomite is mined underground in Europe, Africa, South America and Asia. In one operation in Iceland, where the mineral lies under water, slurried material is transferred by a pipeline to a processing plant...The processing methods for crude material are fairly uniform worldwide. The general procedure...can be schematized as follows: Preliminary size reduction; drying, grinding; dried, fine diatomite; /heated in/ furnace, 800-1000 C; grinding; calcined diatomite; /treated with/ alkaline flux, 1000-1200 C; grinding /to form/ flux-calcined diatomite. Calcination and, even more so, flux calcination yields a considerable amount (up to 65%) of crystalline material (cristobalite).
U.S. Exports

(1985) 1.09X10+11 g
(1992) 1,474,000 tons /Industrial sand and gravel/
(1991) 1,637,000 tons /Industrial sand and gravel/
(1990) 1,155,000 tons /Industrial sand and gravel/
(1989) 2,060,000 tons /Industrial sand and gravel/
(1988) 1,060,000 tons /Industrial sand and gravel/
U.S. Imports

(1985) Less than 4.54X10+8 g
(1992) 181,000 tons /Industrial sand and gravel/
(1991) 91,000 tons /Industrial sand and gravel/
(1990) 73,000 tons /Industrial sand and gravel/
(1989) 35,000 tons /Industrial sand and gravel/
(1988) 43,000 tons /Industrial sand and gravel/
U.S. Production

(1985) 5.78X10+11 g
(1992) Sold or Used: 25,302,000 tons /Industrial sand/
(1991) Sold or Used: 24,541,000 tons /Industrial sand/
(1990) Sold or Used: 26,956,000 tons /Industrial sand/
(1989) Sold or Used: 27,819,000 tons /Industrial sand/
(1988) Sold or Used: 27,207,000 tons /Industrial sand/
Consumption Patterns

(DIATOMITE) 60% IN FILTRATION; OVER 20% AS AN ABRASIVE, IN INDUSTRIAL FILLERS, & AS A LIGHT WEIGHT AGGREGATE; 5% IN INSULATION; UNDER 15% IN MISC APPLICATIONS (INCLUDING IN POZZOLANS, AS AN INERT CARRIER & COATING AGENT) (1974).
Filter aid, 67%; Fillers, 22%; Other, 11% (1985)
【Usage】

Manufacture glass, water glass, refractories, abrasives, ceramics, enamels, in scouring-& grinding-compd, ferrosilicon, molds for castings, decolorizing & purifying oils, petroleum products, etc.

Biomedical Effects and Toxicity

【Therapeutic Uses】
/Exptl Ther/ Previous in vitro studies showing that bioactive glasses support the growth and maturation of rat osteoblast-like cells and promote the expression and maintenance of the osteoblastic phenotype have suggested that there is both a solution-mediated and a surface-controlled effect on cell activity. This study investigated the behavior of human primary osteoblast-like cells cultured in contact with three different bioactive glasses and compared them with amorphous silica (SiO2) used in the form of granules. Osteoblasts synthesize collagen type I, which is subsequently mineralized. Immunoblot and biochemical studies showed increased collagen release from osteoblast-like cells cultured in contact with bioactive glasses over that of controls. Among the three bioactive glasses, 45S5 is the highest inducer of osteoblast-like cell collagen release; moreover, mRNA for type I collagen was stimulated approximately three- to fivefold after 45S5 treatment. 77S bioactive glass similarly increased type I collagen synthesis even though alkaline phosphatase was not higher. These results suggest that 45S5 Bioglass not only induces osteogenic differentiation of human primary osteoblast-like cells, but can also increase collagen synthesis and release. The newly formulated bioactive gel-glass 77S seems to have potential applications for tissue engineering, inducing increased collagen synthesis.
【Biomedical Effects and Toxicity】
...Rats /were exposed/ by inhalation to... silica (particle size 0.5 to 5 m) in the form of Belgian glass sand for periods ranging from 0.5 to 40 hr. The initial deposition of silica was highest in the tracheobronchial ciliated air passages; it also was seen throughout the acini, where the extent of deposition decreased as the respiratory airways proceeded distally. The distribution of particles was not uniform between the different acini, and, 2 to 3 months following cessation of exposure, aggregates were formed, primarily in the proximal alveolar ducts but also in the distal portion of the acini.
Inhalation studies with rats... indicate that the long-term clearance of quartz after inhalation is slow and biphasic, whereas amorphous silica dusts are cleared more rapidly. The absolute amount of silica dust eliminated increased with lung burden, but the efficiency of the elimination was either constant or decreased with time. ...The half-life lung clearance of rats exposed via inhalation to an amorphous silica suspension (Ludox ) at concentrations up to 150 mg/cu m was about 50 days.
A study /in (1983)/, showed that the total silica content in the lungs of guinea pigs exposed by inhalation for up to 2 years to a cristobalite sample or to amorphous silica (at dust concentrations of 150 mg/cu m or 100 mg/cu m , respectively) increased linearly over 21 months, without evidence that lung retention rates changed with time. ...The maximum lung content of cristobalite was only 68 mg/lung, whereas that of amorphous silica was 120 mg/lung. The total amount of accumulated silica varied inversely with the degree of pulmonary damage. /It was/ suggested that silica dust producing cell damage may be more efficiently cleared from the lung than are the less toxic amorphous forms. However, this difference also could be due to different rates of deposition for the two dust forms. The cristobalite sample, which was 45% cristobalite and 55% diatomaceous earth, was significantly coarser (and less likely to deposit in the lungs) than the amorphous silica, which contained 100% diatomaceous earth. Also, tissue changes induced by cristobalite could have altered particle deposition.
In a long-term inhalation study with guinea pigs, ...the amount of silica retained as a result of 8-hr/day exposures to amorphous silica (Hi-Sil 233) /was compared/ with that retained during inhalation of quartz dust for a comparable 12-month period. Guinea pigs that inhaled quartz dust at a concentration of 106 mg/cu m retained between 500 and 600 mg of silica, whereas
Differences in deposition and clearance between quartz and three amorphous silicas, Aerosil 200, Aerosil R 974, and Sipernat 22S, were noted in a subchronic inhalation study with rats... . Aerosil 200 is hydrophilic and is the most widely used form of amorphous silica. Aerosil R 974 is produced by a chemical treatment of Aerosil 200 that transforms the material into a hydrophobic state. Sipernat 22S has the same specific surface area as Aerosil 200. High concentrations of silicon were detected in the lungs and lung-associated lymph nodes of rats exposed to quartz, both at the end of the 13-week exposure period and at all stages of the 1-year postexposure period. Much lower concentrations were detected in the lungs of animals treated with amorphous silicas. Of the groups exposed to amorphous silicas, the highest particulate concentrations were seen in the lungs and lymph nodes of rats exposed to Aerosil R 974 at the end of exposure, with smaller amounts still present at Weeks 13 and 26 postexposure. In most animals, all three amorphous silicas were cleared completely from the lungs by Week 39 of the postexposure period.
Silicon dioxide is slowly absorbed from dusts deposited in lungs, or from material taken orally.

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