Sodium tetraborate
[CAS 1330-43-4]

Identification

• Classification: Inorganic chemical industry >> Inorganic salt >> Boride, borate and perborate
• Name: Sodium tetraborate
• Synonyms: Disodium tetraborate
• Molecular Formula: Na₂B₄O₇
• Molecular Weight: 201.21
• CAS Registry Number: 1330-43-4
• EC Number: 215-540-4
• SMILES: B1(OB2OB(OB(O1)O2)[O-])[O-].[Na+].[Na+]

Properties

• Density: 2.367 g/mL (Expl.)
• Melting point: 741 °C (Expl.)
• Boiling point: 1575 °C (Decomposes) (Expl.)
• Solubility: water: 4.0 g/100g (Expl.)

Safety Data

• Hazard Symbols: GHS08 Danger
• Risk Statements: H360FD
• Safety Statements: P203-P280-P318-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Reproductive toxicity	Repr.	1B	H360
Eye irritation	Eye Irrit.	2	H319
Reproductive toxicity	Repr.	1B	H360FD
Reproductive toxicity	Repr.	2	H360
Acute toxicity	Acute Tox.	4	H302
Reproductive toxicity	Repr.	1A	H360
Serious eye damage	Eye Dam.	1	H318
Acute toxicity	Acute Tox.	4	H332
Reproductive toxicity	Repr.	1B	H360Fd
Reproductive toxicity	Repr.	1B	H360FD

chemBlink Chemical Story

Sodium tetraborate, CAS 1330-43-4, is the anhydrous sodium borate Na2B4O7, often called anhydrous borax or borax glass. PubChem records a molecular weight of 201.2. This CAS identity matters because the familiar name borax is also widely used for hydrated sodium tetraborates, especially the decahydrate; the anhydrous material and its hydrates have different formula weights and solid-state compositions.

Borate chemistry is built around boron-oxygen units that can form rings and extended networks. In glass formation, sodium tetraborate contributes boron-oxygen network chemistry while sodium acts as a network modifier. Borates are therefore important in glass, ceramic, enamel and glaze formulations, where they influence melting behavior, thermal expansion and chemical durability.

Sodium borates are also useful as buffering and fluxing materials. In analytical and metallurgical chemistry, borate fluxes can help convert refractory inorganic samples into homogeneous melts for subsequent analysis. In aqueous chemistry, borate species participate in acid-base equilibria that make borate buffers useful over appropriate pH ranges.

The compound illustrates why hydration state matters in chemical databases. A material called sodium tetraborate may be anhydrous, pentahydrate, decahydrate or another hydrate depending on specification. Heating hydrated borax removes water and eventually produces an anhydrous glassy borate, but CAS-specific records should not silently treat all these solids as identical.

References:
1. PubChem, Sodium tetraborate, CID 10219853, CAS 1330-43-4.
2. Greenwood NN, Earnshaw A. Chemistry of the Elements. 2nd ed. Butterworth-Heinemann, 1997.
3. Doremus RH. Glass Science. 2nd ed. Wiley, 1994.

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