Silica (CAS 7631-86-9) — Citrus Functional additive Note Fragrance Ingredient
Silica
CAS 7631-86-9
What Is Silica?
Silica is a synthetic powder commonly used in cosmetics and personal care products as an absorbent, thickener, or anti-caking agent. You’ll find it in powdered makeup, dry shampoos, and some fragrance formulations where it helps control oiliness. While odorless itself, silica plays a crucial role in product performance by improving texture and extending fragrance longevity when used as a carrier material or in encapsulation systems.
Safety Profile
GENERALLY SAFEWhat Does Silica Smell Like?
Silica is completely odorless and tasteless, serving purely functional roles in fragrance formulations. As an amorphous solid, it neither contributes nor interferes with scent profiles. Its microscopic structure makes it excellent for absorbing oils and slowly releasing volatile compounds, subtly modulating fragrance performance without altering olfactory characteristics.
2D Molecular Structure
SMILES: O=[Si]=O
Chemistry, Properties & Perfumer Guide
The Chemistry
Silica (SiO₂) exists in multiple crystalline and amorphous forms, with cosmetic-grade silica typically being fumed or precipitated amorphous silica. Produced through vapor-phase hydrolysis of silicon tetrachloride or by acid precipitation from sodium silicate solutions, its high surface area (50-600 m²/g) and porosity make it valuable for fragrance applications. The material’s hydrophilic or hydrophobic properties can be tailored through surface treatment with silanes.
Physical & Chemical Properties
| Appearance | White amorphous powder |
|---|---|
| Density | 2.2 g/cm³ |
| Melting Point | 1713 °C |
Perfumer Guide
| Application | Typical % | Range | Notes |
|---|---|---|---|
| Powder Fragrances | 5-20% | Up to 50% | Absorbs and stabilizes fragrance oils |
| Encapsulation Systems | 10-30% | 5-60% | Carrier for controlled release |
Classic Accords
Tip: Use hydrophobic silica for oil-based fragrances to prevent clumping and improve flow properties.
Alternatives & Comparisons
Natural alternative with similar absorbent properties but different texture and opacity characteristics.
Biodegradable option for powder formulations, though with less oil absorption capacity than silica.
Safety, Regulatory & Sustainability
⚠ Regulatory Disclaimer
General reference only. Consult current IFRA Standards Library before formulating.
IFRA Status
No IFRA restrictions – classified as non-toxic and non-sensitizing.
RIFM Assessment
RIFM considers silica safe for all cosmetic applications with no sensitization concerns.
Sustainability
While silica itself is abundant (derived from sand), energy-intensive production processes for cosmetic-grade materials raise environmental considerations. Some manufacturers now offer bio-silica derived from rice husk ash as a more sustainable alternative. Proper dust control during handling is crucial to prevent respiratory exposure in production facilities.
Explore Silica
Browse essential oils and aroma compounds.
Browse on iHerb →Affiliate disclosure: we may earn a small commission at no extra cost to you.
References
- Cosmetic Ingredient Review (2018). Safety Assessment of Silica and Related Materials. CIR Report
- European Chemicals Agency (2020). Silicon Dioxide REACH Registration Dossier. ECHA
Data: PubChem (NIH), PubMed, RIFM, IFRA. Last reviewed: Apr 2026.
Report a data errorIngredient Data Sheet
CAS 7631-86-9Physical Properties
| Molecular Weight | 60.084 g/mol🔬 PubChem |
| Vapor Pressure | 0 mmHg @ 25°C📊 OPERA |
| SMILES | O=[Si]=O🔬 PubChem |
Physical data: PubChem (NIH/NLM), U.S. EPA CompTox Dashboard, EPA OPERA models, RDKit. Odor & flavor: Arctander (Perfume & Flavor Chemicals), Fenaroli's Handbook of Flavor Ingredients, Leffingwell. Thresholds: van Gemert (Compilations of Odour Threshold Values). Regulatory: IFRA Standards 51st, FEMA GRAS. Trade names: Surburg (Common Fragrance & Flavor Materials). All data compiled and cross-referenced for perfumertools.com.
Physicochemical Properties
DTXSID: DTXSID1029677
Physical Properties
| Molecular Weight | 60.083 g/mol🔬 EPA CompTox |
| Density | 2.15 g/cm^3🔬 EPA CTX |
| Boiling Point | 2230 °C🔬 EPA CTX |
| Melting Point | 1685.75 °C🔬 EPA CTX |
Partition & Solubility
| LogP (Octanol-Water) | -0.618 dimensionless💻 Computed |
| Water Solubility | 0.002 mol/L🔬 EPA CTX |
Transport Properties
| Vapor Pressure | 10.13 mmHg🔬 EPA CTX |
Molecular Descriptors
| Topological Polar Surface Area | 34.14 Ų💻 Computed |
| H-Bond Donors | 0 count💻 Computed |
| H-Bond Acceptors | 2 count💻 Computed |
| Rotatable Bonds | 0 count💻 Computed |
| Aromatic Rings | 0 count💻 Computed |
| Molar Refractivity | 7.13 cm^3/mol💻 Computed |
Data Sources:
🔬 EPA Experimental data from U.S. EPA CompTox Chemicals Dashboard & CTX APIs. 📊 OPERA Predicted using EPA's OPERA QSAR models. 💻 Computed Calculated from SMILES using RDKit.
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