Mineral Fillers & Pigments Available — Bulk Only

Aluminum Hydroxide (ATH, Alumina Trihydrate)

ATH
CAS 21645-51-2 · Formula AlH3O3 · MW 78.004 g/mol

A halogen-free mineral flame retardant that quenches fire by releasing water as it decomposes. In plastics, rubber, and latex foams it releases water on heating to retard flame and suppress smoke.

Safety Data Sheet
HS Code
2818.30
At a Glance
Material Family
Mineral Fillers & Pigments
Record Type
Pure compound
Primary Role
Color / Pigmentation · Flame Retardancy
Functional Roles
CI 77002
COLORANT
Applications & Use Cases
  • Flame retardant: Halogen-free flame retardant for plastics, rubber, and latex foam.
  • Smoke suppressant: Smoke suppressant in polymer compounds.
  • Filler: Functional filler in paper, plastics, and rubber.
  • Abrasive: Soft abrasive for brass and plastics.
  • Desiccant: Desiccant powder.
Physical Properties
Physical Description
White solid in various forms; White odorless granules; Slightly soluble in water
Appearance
Usually obtained in white, bulky, amorphous powder
Melting Point
300 °C
Solubility
Practically insoluble in water, but soluble in alkaline aqueous solutions or in HCl, H2SO4 and other strong acids in the presence of some water
Density
White, gelatinous precipitate. Constants variable with the composition, density approximately 2.4. Insoluble in water and alcohol, soluble in acid and alkali. /Aluminum hydroxide gel/
Vapor Pressure
Vapor pressure, Pa at 20 °C:
Refractive Index
Monoclinic crystal system; Mohs hardness: 3; Index of refraction: 1.57 (least index); 1.57 (intermediate index); 1.59 (greatest index) /Gibbsite/
Dissociation Constants
Aluminum hydroxide is capable of reacting as either an acid or a base
Safety & Handling
Full SDS available on request

A grade-specific Safety Data Sheet (SDS) — with the complete hazard classification, handling precautions, and transport information — is supplied with every shipment and available on request. Confirm all safety and regulatory details against the SDS for your specific grade.

HS / Tariff Classification
Harmonized System (HS) Code — 6-digit international heading
2818 . 30
Chapter 28
Inorganic chemicals; compounds of precious metals and rare-earth metals
Heading 28.18
Internationally harmonized (WCO HS)
Subheading 2818.30
6-digit international code — national tariff line adds further digits
Chemical Identity
CAS Number
21645-51-2
Molecular Formula
AlH3O3
Molecular Weight
78.004 g/mol
IUPAC Name
aluminum trihydroxide
INCI Name
CI 77002
PubChem CID
InChI Key
WNROFYMDJYEPJX-UHFFFAOYSA-K
Synonyms & Trade Names
Hydrated alumina Amphojel aluminum hydrate Dried aluminium hydroxide Aluminum hydroxide, dried ALternaGEL Aluminium hydroxide, dried Alu-Cap Aluminum hydroxide gel, dried Aluminium hydroxide gel, dried Alcoa C 30BF Hydroxyde d' aluminium Aluminum(III) hydroxide aluminium(III) hydroxide WinGel Di-mu-hydroxytetrahydroxydialuminum Alum Adjuvant Basalgel Dermadrox Sarpep
Full Description

Aluminum hydroxide (ATH, CAS 21645-51-2) is an inorganic compound used as a flame retardant, smoke suppressant, and functional filler. In plastics, rubber, and latex foams it releases water on heating to retard flame and suppress smoke. It is also used as a filler in paper and as a desiccant and soft abrasive.

Frequently Asked Questions

What is aluminum hydroxide used for?

Aluminum hydroxide (ATH, CAS 21645-51-2) is mainly used as a halogen-free flame retardant and smoke suppressant in plastics, rubber, and latex foams, releasing water on heating to retard flame. It also serves as a functional filler in paper and polymers and as a soft abrasive and desiccant.

What is the common name for aluminum hydroxide?

In industrial use it is commonly called ATH (alumina trihydrate or aluminum trihydroxide). The formula is Al(OH)3 (AlH3O3), CAS 21645-51-2.

How does aluminum hydroxide work as a flame retardant?

On heating, ATH undergoes endothermic decomposition, absorbing heat and releasing water vapor that dilutes combustible gases and suppresses smoke. This makes it a widely used halogen-free flame-retardant filler for polymer compounds.

Is aluminum hydroxide water soluble?

No. Aluminum hydroxide is essentially insoluble in water, which is why it performs as a stable particulate filler and flame-retardant additive dispersed within polymer and rubber matrices.

What grades and packaging of aluminum hydroxide are available in bulk?

ATH is supplied in a range of particle sizes for filler versus flame-retardant applications; specify your target grade and we confirm availability. RawSource ships bulk in bags and palletized quantities under HS 2818.30, with CoA and SDS on request.

Disclaimer. Information on this page — including properties, identifiers, hazard, transport (DOT/UN) and tariff (HS) classifications, and applications — is provided for general reference and is compiled from authoritative public sources (e.g. PubChem/ECHA, 49 CFR 172.101, the Harmonized Tariff Schedule). Values are typical and are not a guaranteed specification; the Certificate of Analysis (CoA) for the lot purchased governs. Products are sold for industrial and professional use only. Nothing here is a medical, health, or efficacy claim or advice. Always consult the current Safety Data Sheet (SDS) before handling, storage, transport or disposal, and confirm regulatory status, classification and suitability for your application and jurisdiction. Hazard, transport and tariff classifications must be verified for your specific shipment. RawSource makes no warranty, express or implied, and assumes no liability for use of this information. Trademarks. Third-party trademarks and brand names are the property of their respective owners; any reference is nominative — used only to identify a comparable product — and does not imply affiliation with, sponsorship by, or endorsement by the trademark owner.