Name: Hectorite
CAS No: Hectorite [12173-47-6]
None adopted.
Hector clay; Hectabrite AW; Hectabrite DP; Ghassoulite; Laponite; SHCa-1; Strese & Hofmann’s Hectorite.
Hectorite [12173-47-6]
Na0.3(Mg,Li)3Si4O10(F,OH)2 383 Hectorite is a mineral with an approximate empirical formula owing to the variability in cation substitution; see Table I.
Hectorite is a natural mineral clay, obtained from altered volcanic ash with a high silica content. It is composed of two tetrahedral layers formed by phyllosilicate sheets and one octahedral layer. The apical oxygens of the two tetrahedral sheets project into the octahedral sheet. It is structurally similar to talc but differs by substitution, mainly in the octahedral layer. Common impurities include aluminum, calcium, chlorine, iron, potassium, and titanium.
Hectorite is used widely in pharmaceutical preparations as an absorbent, emulsifier, stabilizer, suspending agent, thickener, and viscosity-controlling agent.(2) Hectorite is a component of other naturally occurring clays and hence may be suitable for use in similar pharmaceutical formulation applications as an adsorbent, oil-in-water emulsifying agent, suspending agent, or viscosity-increasing agent.(3) It is also available as a synthetic material. Hectorite is used to modify the thixotropic behavior of pharmaceutical dispersions(4) and for stabilizing oil-inwater emulsion bases.(5,6) When combined with an appropriate cation, hectorite exhibits properties suitable for use as a contrast agent.(7)
Hectorite is a naturally occurring 2 : 1 phyllosilicate clay of the smectite (montmorillonite) group and is a principal component of bentonite clay. Hectorite occurs as an odorless, white to creamcolored, waxy, dull powder composed of aggregates of colloidalsized lath-shaped crystals.
—
Cation exchange capacity 43.9 meq/100 g Crystal data Space group C2/m, a = 5.2, b = 9.16, c = 16.0, b 998. Density (true) 2.5 g/cm3 Hardness (Mohs) 1–2 Moisture content Hectorite loses 10% of water up to 1508C; 2% above 1508C. Refractive index na= 1.49; nb= 1.50; ng= 1.52 (biaxial –). Specific surface area 63.2m2/g. Hectorite swells on the addition of water.
Hectorite is a stable material and should be stored in a cool, dry place.
Contact between hectorite and hydrofluoric acid may generate heat.
Naturally occurring hectorite is mined from weathered bentonite deposits. It is further processed to remove grit and impurities so that it is suitable for pharmaceutical and cosmetic applications.
Hectorite is a natural clay mineral that is not considered acutely toxic; therefore no toxicity values have been established. However, hectorite may contain small amounts of crystalline silica in the form of quartz. Dust can be irritating to the respiratory tract and eyes,(8) and contact with this material may cause drying of the skin. Chronic exposure to crystalline silica may have adverse effects on the respiratory system. EU labeling states that the material is not classified as dangerous.
Observe normal precautions appropriate to the circumstances and quantity of material being handled. Avoid generating and breathing dust, and use eye protection. For dusty conditions, eye protection, gloves, and a dust mask are recommended. The occupational exposure limits for hectorite are 5 mg/m3 (respirable) PEL-TWA, 3 mg/m3 (respirable) TLV-TWA, and 10 mg/m3 (inhalable dust) TLV-TWA.
Reported in the EPA TSCA Inventory.
Attapulgite; bentonite; kaolin; magnesium aluminum silicate; quaternium 18-hectorite; saponite; stearalkonium hectorite; talc. Quaternium 18-hectorite CAS numbers [71011-27-3]; [12001-31-9]. Synonyms Bentone 38. Comments Quaternium 18-hectorite is used in cosmetics as a viscosity-controlling agent. It does not contain crystalline silica. The EINECS numbers for quaternium 18-hectorite are 234-406- 6, and 234-406-6. Stearalkonium hectorite CAS numbers [94891-33-5]; [71011-26-2]. Synonyms Bentone 27. Comments Steralkonium hectorite is used in cosmetics as a viscosity-controlling agent. Reported in the EPA TSCA Inventory. The EINECS numbers for stearalkonium hectorite are 305- 633-9, and 275-126-4.
Polyethylene glycols 400, 1500, and 4000 have been shown to increase the consistency of hectorite dispersions.(9) Synthetic hectorite has been conjugated with block copolymers of polyethylene glycol to form hybrid nanocrystal drug carriers.(10) The EINECS number for hectorite is 235-340-0.