Borax

Product Overview

Borax, commercially dominated by disodium tetraborate decahydrate (CAS 1303‑96‑4), is a bulk basic inorganic borate raw material. Three major commercial grades are available: decahydrate borax, pentahydrate borax and anhydrous borax, among which decahydrate borax is the mainstream general‑purpose specification. Pure product appears as colourless transparent columnar crystals or white crystalline powder, odourless with salty and slightly bitter taste. It remains stable under normal temperature and dry conditions, features good water‑solubility, and undergoes gradual weathering and water loss in dry air.

Borax dissolves readily in water and glycerol to form weakly‑alkaline aqueous solutions. It is slightly soluble in ethanol and insoluble in most organic solvents. It exhibits excellent performance in buffer fluxing, decontamination‑emulsification, bacteriostasis & anticorrosion, ceramic fluxing, glass clarifying and metal complexing. It serves as an indispensable boron source for glass, ceramics, daily‑use chemicals, metallurgy and fine‑chemical industries. Multiple product grades are classified by crystal‑water content, purity and impurity control to meet civil, general‑industrial and high‑end fine‑chemical working conditions.

Basic Parameters

Production Processes

Carbonate‑Alkali Process (Primary Process in China)

Roasting Activation: Boron‑magnesium ore (main component: Mg₂B₂O₅·H₂O) is crushed and roasted to improve boron activity.

Carbonolysis Reaction: Roasted ore powder mixes with sodium carbonate (Na₂CO₃) solution. Carbon dioxide (CO₂) is injected under elevated pressure and temperature.
Reaction:
2MgO·B₂O₃ + Na₂CO₃ + 2CO₂ + H₂O → 2NaBO₂ + 2Mg(HCO₃)₂
(Sodium metaborate enters liquid phase)

Overall reaction:
Mg₂B₂O₅·H₂O + Na₂CO₃ + CO₂ → 2NaBO₂ + 2MgCO₃↓ + H₂O

Filtration & Separation: Insoluble magnesium carbonate (MgCO₃) residue is filtered off.

Carbonation & Crystallization: CO₂ is further introduced into sodium metaborate filtrate to reduce alkalinity and precipitate borax:
4NaBO₂ + CO₂ + 10H₂O → Na₂B₄O₇·10H₂O↓ + Na₂CO₃

Centrifugation & Drying: Borax crystals are separated and dried to obtain finished product.

Pressurized Alkaline Hydrolysis Process

Alkaline Digestion: Ground boron‑magnesium ore reacts with sodium hydroxide (NaOH) solution under high temperature and pressure:
Mg₂B₂O₅·H₂O + 2NaOH → 2NaBO₂ + 2Mg(OH)₂↓

Filtration: Magnesium hydroxide precipitate (Mg(OH)₂) is removed.

Carbonation Crystallization: CO₂ is fed into filtrate for crystallization:
4NaBO₂ + CO₂ + 10H₂O → Na₂B₄O₇·10H₂O↓ + Na₂CO₃

Sulfuric‑Acid Process (Traditional, mostly phased‑out after 1961)

Acid Digestion: Boron‑magnesium ore reacts with sulfuric acid to produce crude boric acid:
Mg₂B₂O₅·H₂O + 2H₂SO₄ → 2H₃BO₃ + 2MgSO₄

Separation & Purification: Magnesium sulfate (MgSO₄) is filtered to yield crude boric acid.

Neutralization & Crystallization: Crude boric acid is neutralized with soda ash to generate borax:
4H₃BO₃ + Na₂CO₃ + 3H₂O → Na₂B₄O₇·10H₂O + CO₂↑

Product Grades

Grading is application‑oriented. Industrial grades are divided into Premium Grade and First‑Class Grade per national standards. Pharmaceutical grade meets pharmacopoeia specification with content 99.0%‑103.0%. For Chinese medicinal use, borax is categorized by processing form: Borax Block, Borax Lump and Borax Powder.

Industrial‑Grade Borax
Industrial borax complies with GB/T 537‑2009. Two grades are defined based on main component and impurity indexes.

Premium Grade: disodium tetraborate decahydrate ≥99.5%; carbonate ≤0.1%; water‑insoluble matter ≤0.04%; sulfate ≤0.1%; chloride ≤0.03%; iron ≤0.002%.

First‑Class Grade: disodium tetraborate decahydrate ≥95.0%; carbonate ≤0.2%; water‑insoluble matter ≤0.04%; sulfate ≤0.2%; chloride ≤0.05%; iron ≤0.005%.

Commercially available industrial borax is mostly First‑Class Grade (95% content), sold by tonne with labels such as "Industrial Grade First‑Class, 95%".

Pharmaceutical‑Grade Borax
Compliant with Chinese Pharmacopoeia. Assay of disodium tetraborate decahydrate shall be within 99.0%‑103.0%. This range guarantees purity and avoids artificially elevated readings caused by dehydration. Pharmaceutical grade imposes stricter limits for heavy metals, chlorides and other impurities with test methods fully aligned with pharmacopoeia requirements.

Specifications for Borax as Chinese Medicinal Material
Subject to association standard T/CACM 1021.22‑2018, classified by processing method.

Borax Block: crystallized blocks subdivided into Grade‑Ⅰ and Grade‑Ⅱ by size, colour and transparency with superior quality.

Borax Lump: bulk crystallized commodity with comparable quality to Borax Block.

Borax Powder: ground raw medicinal material; susceptible to contamination and easily confused with industrial borax powder; slightly inferior in quality to block‑form products.

Upstream‑Downstream Industrial Chain

As a fundamental inorganic borate feedstock, borax features a well‑structured, clearly‑divided closed‑loop industrial chain.

Upstream raw materials: natural boron ore, boron‑magnesium ore, sodium carbonate (soda ash), industrial purified water, impurity‑removal settling agents, recrystallization auxiliaries.

Downstream applications: glass clarifying flux, ceramic glaze additive, metallurgical welding flux, emulsifier for detergent, boron micronutrient fertilizer for agriculture, intermediate for fine borate chemicals, buffering agent for wastewater treatment, bacteriostatic & anticorrosive raw material.

Safety, Storage & Transportation

Borax is a low‑toxic general inorganic salt. Non‑flammable, non‑explosive and non‑corrosive. It is not classified as hazardous chemical and shall be handled as general chemical cargo. Powder and aqueous solution cause mild irritation to skin, eyes and respiratory mucosa. Ingestion of large quantities leads to toxic risks. Proper personal protection is mandatory; ingestion must be strictly prohibited.

Storage Requirements
Store in dedicated dry, cool, ventilated and clean chemical warehouse. Keep packages fully sealed to isolate dry airflow and high temperature so as to prevent weathering, water loss and caking. Stack separately; never co‑store with strong acids, strong oxidants or toxic substances to avoid cross‑contamination and chemical reactions. Keep away from food and feed to prevent accidental ingestion.

Transportation Requirements
Follow general chemical cargo regulations. Ensure rain‑proofing, moisture‑proofing, sun‑shading and package integrity during transit. Do not co‑transport with strong acids, odorous toxic goods, food or feed to prevent contamination and quality deterioration.

Safety Characteristics
Physicochemically stable under sealed ambient‑temperature conditions. Powder dust mildly irritates mucosa. Concentrated aqueous solutions are non‑corrosive to skin, though prolonged contact may cause skin dryness. Ingestion and excessive long‑term contact are forbidden. Standard PPE including dust‑proof respirators and labour gloves are required; maintain good ventilation at work site. No major safety hazards exist under proper storage, handling and operation.

FAQ

Q：How to prevent borax from weathering and caking during storage?
A：Borax tends to weather and lose water in dry ambient air, resulting in whitening, loose caking and decline of active content. Key preventive measures: maintain fully sealed packaging against air leakage; keep warehouse cool and constant‑temperature; avoid strong dry air convection; reduce frequent window‑opening to slow dehydration; prevent high‑temperature stacking and direct sunlight. Product properties can remain stable long‑term under qualified sealed storage.

Q：What are the application differences between industrial‑grade and high‑purity refined borax?
A：They share identical chemical composition, differing mainly in impurity control precision and applicable scenarios. Industrial‑grade borax meets basic specifications with good cost‑performance for high‑volume general‑industrial applications with higher impurity tolerance. Refined high‑purity borax is produced via multiple recrystallization steps with strict trace‑impurity control and high aqueous‑solution cleanliness, designed for demanding scenarios such as fine chemicals, high‑end building materials and precision manufacturing. China boasts abundant boron resources and mature complete borax manufacturing chain. Leveraging advanced ore‑purification and temperature‑controlled crystallization technologies, China achieves large‑scale production with diversified specifications, stable quality and competitive cost. It can satisfy domestic demand for both general‑industry and high‑end refined products as well as overseas export orders, acting as one of the world's core borax production and supply bases.

Q：What are the major advantages of Chinese‑produced borax versus imported borax?
A：① Independent process technology: The domestically‑adopted carbonate‑alkali process is tailored for local boron‑magnesium ore resources. Production technologies are fully independent and controllable, lowering external supply‑chain disruption risks.
② Full‑range specifications: Domestic manufacturers produce First‑Class / Premium industrial grades, pharmacopoeia‑grade and high‑purity refined products, supporting customized index requirements.
③ Delivery & technical service advantages: Short lead time from domestic origins, together with local technical support to rapidly meet process‑commissioning demands from various industries.
④ Cost advantage: Scale effects from complete industrial chain deliver outstanding cost‑performance at equivalent quality, with capacity to fulfil overseas export orders.