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Complete Guide to Silica CAS Numbers
Most hydrophobic fumed silica products use CAS 112945-52-5 as the standard identifier, regardless of manufacturer. However, specific models may have unique CAS numbers based on their surface treatment and production processes:
Primary CAS Number for Food-Grade Silica:
7631-86-9 (Universal identifier for all forms of food-grade silica)
International Food Codex Number:
INS 551 or E551 (Global standard number for food additives)
Executive Standard:
GB 25576-2020 (National Food Safety Standard of the People's Republic of China)
What is a CAS Number?
A CAS Registry Number (CAS RN) is a unique numerical identifier assigned to each chemical substance by the Chemical Abstracts Service (CAS) of the United States. It serves as a globally recognized "identification card" for chemical substances, enabling precise identification in scientific literature, databases, and commercial transactions.
1. Official Classification of Food-Grade Silica (Per GB 25576-2020 Standard)
| Category | Name | CAS Number | Production Process | Silica Content (%) | Loss on Drying (%) | Main Applications |
| Class I | Fumed Silica | 112945-52-5 | Hydrolysis of chlorosilane in an oxygen-hydrogen flame | ≥99.3 | ≤2.5 | High-end food additives, health product carriers, anti-caking agents |
| Class II | Hydrated Silica Gel | 112926-00-8 | Reaction of sodium silicate solution with acid (gel method) | ≥99.0 | ≤70.0 | Food moisture absorbents, enzyme carriers |
| Class III | Precipitated Silica | 112926-00-8(7631-86-9) | Reaction of sodium silicate solution with acid (precipitation method) | ≥96.0 | ≤7.0 | Anti-caking agents for common powdered foods, toothpaste abrasives |
2. Hydrophilic Fumed Silica
CAS Number:
112945-52-5 (Primary identifier)
Aliases:
Fumed Silica (Industrial common name)
Nano-silica
Aerosil Series (e.g., A300, A200)
Characteristics:
Particle size: 10-30nm; Specific surface area: 100-400m²/g
High purity (≥99.8%), almost free of crystalline silica
Excellent fluidity and anti-caking performance
3. Hydrophobic Fumed Silica
General CAS Number:
112945-52-5 + Special treatment identifier
Explanation:
Most hydrophobic fumed silica products use CAS 112945-52-5 as the standard identifier, regardless of manufacturer. However, specific models may have unique CAS numbers based on their surface treatment and production processes:
AEROSIL R812S: Unique CAS 68909-20-6
AEROSIL R202 (Treated with dimethylpolysiloxane): CAS 67762-90-7
AEROSIL R974 (Treated with dimethyldichlorosilane): CAS 68611-44-9
AEROSIL R104/R106 (Treated with octamethylcyclotetrasiloxane): CAS 68583-49-3
4. Application Comparison of Silica Types
Class I (Fumed Silica) – Optimal Applications:
High-end powdered foods: Milk powder, protein powder, cocoa powder
Pharmaceutical field: Capsule fillers, tablet disintegrants
Health products: Vitamin carriers, probiotic protectants
Products requiring high fluidity: Seasonings, soup mixes
Class II (Hydrated Silica Gel) – Optimal Applications:
High moisture absorption scenarios: Food moisture absorbents
Liquid adsorbents: Adsorbing phosphorus and impurities in edible oils, beer, beverages, etc.
Class III (Precipitated Silica) – Optimal Applications:
Anti-caking agents for common powdered foods: Solid beverages, flavors, seasoning powders, etc.
Daily chemical products: Toothpaste abrasives, thickeners
Price-sensitive applications: Animal feed additives
5. Purchase & Usage Guide
1. Food-Grade Verification:
Must comply with GB 25576-2020 standard; labeled "Food Additive" on packaging
Imported/exported products require FDA or EU certification
2. Type Selection:
Choose Class I for high-end applications: Products requiring high fluidity and purity
Choose Class III for cost-effectiveness: Common food anti-caking, daily chemical products
Choose hydrophobic type for special needs: Moisture-proof and water-resistant scenarios
3. Safety Precautions:
Food-grade silica is non-toxic, but inhalation of dust may irritate the respiratory tract
Store in a dry place; avoid contact with strong alkaline substances
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