Salts & Minerals
REACH
Sodium tetraborate
CAS Number
1330-43-4
EC Number
215-540-4
E Number
E285
What is Sodium tetraborate?
Sodium tetraborate (CAS 1330-43-4), also known by its E-number E285, is the anhydrous form of borax — a mineral salt used as a preservative and buffering agent.
Where is Sodium tetraborate used?
- Building and construction: flame retardancy and fungal resistance in wood treatments and insulation materials
- Textile and leather: pH control in bath formulations and improved uptake of dyes and finishing agents
- Water treatment: buffering compound that stabilizes pH in industrial process water
- Food contact and packaging: preservative at permitted E285 levels in regulated markets
- It also functions as a flame retardant and cleaning booster.
Good to know: Its anhydrous form offers a higher boron content and lower moisture contribution compared to hydrated grades, which matters for formulators managing water activity.
Commercial specifications
- Purity typically 99% or higher
- Packaging from 25 kg bags to bulk quantities
Other Names (Synonyms)
sodium borate anhydrous|disodium tetraborate, anhydrous|anhydrous borax|Boron sodium oxide (B4Na2O7)|Borax glass|Sodium Tetraborate, Anhydrous|Sodium biborate|Borax Anhydrous|E285
What are the physical properties of Sodium tetraborate?
Melting Point 741 °C
Boiling Point 1571 °C
Density 2.367 g/cm³
Flash Point 1575°C
Appearance Borax is a noncombustible (an inherent fire retardant), bluish-gray or green, odorless crystalline powder or granules.
Color White
Form Solid
Water Solubility 26 g/L (20 ºC)
Vapor Pressure 7.3 hPa (1200 °C)
Refractive Index 1.501
pH 9.0-10.5 (25℃, 0.1M in H2O)
How is Sodium tetraborate classified and handled safely? Learn More
Danger
GHS08· Health Hazard GHS07· Irritant
Hazard Statements
H302 Harmful if swallowed
H315 Causes skin irritation
H319 Causes serious eye irritation
H320 Causes eye irritation
Precautionary Statements
P203 Obtain, consult and follow expert instructions for use.
P260 Do not breathe dust/fume/gas/mist/vapours/spray.
P261 Avoid breathing dust/fume/gas/mist/vapours/spray.
P264 Wash … thoroughly after handling.
Which trade and regulatory codes apply to Sodium tetraborate?
HS Code 28401100
UN Number 1760
ADR Class 8
Packing Group II
Storage Class 6.1D - Non-combustible acute toxic Cat.3
toxic hazardous materials or hazardous materials causing chronic effects
WGK (Germany) 1