Magnesium Chloride Hexahydrate Specification: The Complete Industrial Buyer’s Guide
For procurement managers and chemical engineers, a clear magnesium chloride hexahydrate specification is the first line of defense against costly supply chain errors. Whether you’re sourcing for de-icing, dust control, fireproofing boards, or magnesium metal production, the chemical’s purity, physical form, and trace impurities directly impact operational efficiency and end-product quality. This guide unpacks every critical parameter you need to evaluate—from molar mass and solubility to industry-specific grades and supplier reliability—so you can secure a consistent, high-performance magnesium chloride supply.
What is Magnesium Chloride Hexahydrate?
Magnesium chloride hexahydrate (MgCl₂·6H₂O) is the most common hydrated form of magnesium chloride. It appears as colorless, deliquescent flakes or granules with a bitter saline taste. The compound readily absorbs moisture from the air, which makes proper packaging and storage essential. In the industrial market, hexahydrate flakes dominate because they offer a practical balance between high magnesium chloride content and stable handling characteristics. Anhydrous magnesium chloride powder and liquid brine solutions are also available for specific processes like molten salt electrolysis or dedusting applications.
Understanding the magnesium chloride product range begins with recognizing that the hexahydrate form is not simply a “wet” version—it is a distinct crystalline solid with its own thermal behavior and application profile. When heated above 118°C, it gradually loses water of crystallization, eventually converting to anhydrous MgCl₂. This dehydration behavior is crucial in fireproofing board production, where controlled water release provides passive fire resistance.
Magnesium Chloride Physical Properties Every Buyer Must Know
A robust magnesium chloride hexahydrate specification sheet includes several fundamental physical constants. Familiarity with these values helps you cross-check supplier data and ensure the product meets process requirements.
- Molar mass (magnesium chloride molar mass): 203.30 g/mol for the hexahydrate (MgCl₂·6H₂O). The anhydrous form has a molar mass of 95.21 g/mol, but industrial buyers typically work with the hydrated value when calculating usage rates.
- Appearance: White to off-white flakes, granules, or crystalline powder.
- Odor: Odorless.
- Density: Approximately 1.57 g/cm³ at 20°C for hexahydrate flakes.
- Melting point: Decomposes at 118°C (dehydration); after full dehydration, melts at 714°C.
- Solubility in water: Highly soluble—up to 167 g/100 mL at 20°C, forming a clear, slightly acidic solution (pH 5–7 for a 5% solution).
- Hygroscopicity: Extremely hygroscopic; flakes will absorb moisture above ~40% relative humidity, so sealed packaging is mandatory.
These magnesium chloride physical properties are not mere academic data points. For a dust control contractor, the high solubility and hygroscopic nature mean the product can draw moisture from the air to keep road surfaces damp longer, reducing water truck frequency. For a fireproofing board manufacturer, the decomposition temperature window dictates the thermal resistance performance of the final board.
Typical Commercial Specifications for Magnesium Chloride Hexahydrate
When reviewing a supplier’s certificate of analysis, look for these core parameters that define a commercial-grade magnesium chloride hexahydrate specification:
- Purity (as MgCl₂·6H₂O): ≥ 99% for high-purity industrial grades; standard grades may range 95–98%. Hailei Chemical’s product achieves up to 46% MgCl₂ content (equivalent to high hexahydrate purity).
- Magnesium chloride content (as MgCl₂): Minimum 46% w/w for hexahydrate flakes. This directly correlates to the active component for de-icing and chemical synthesis.
- Water insolubles: ≤ 0.1%, ensuring no clogging in spray nozzles or reactor fouling.
- Sulfate (SO₄²⁻): ≤ 0.1%, critical for food-grade and electrolytic applications where sulfate can interfere with coagulation or metal purity.
- Calcium (Ca²⁺): ≤ 0.1%, important for de-icing brine compatibility and preventing scaling.
- Iron (Fe³⁺): ≤ 0.005%, particularly vital for fireproofing board color stability and food processing.
- Heavy metals (as Pb): ≤ 10 ppm for industrial grades, even lower for food-grade (meeting FCC or USP standards).
- pH (5% solution): 5.0–7.0.
Beyond purity, the physical form matters. Flakes are preferred for de-icing because they dissolve more slowly than powder, providing longer-lasting traction and ice suppression. Powdered hexahydrate is used where rapid dissolution is needed, such as in brine preparation. Granular forms offer dust-free handling. When discussing your magnesium chloride hexahydrate specification with a supplier, always specify the desired particle size distribution to match your application equipment.
Industry-Specific Grades and Standards
The same chemical serves vastly different industries, and each demands its own nuance in a magnesium chloride hexahydrate specification.
De-icing and Dust Control Grade
For road and airport de-icing, the primary metric is effective temperature range. Magnesium chloride brine works down to -33°C, outperforming sodium chloride (-9°C) and calcium chloride (-29°C). A de-icing contractor should look for a high MgCl₂ content (≥46%), low calcium to minimize scaling on equipment, and consistent flake size for calibrated spreaders. Often, this grade contains a slight excess of magnesium oxide to buffer pH and reduce corrosion, making it less aggressive to concrete and steel than other chloride salts.
Fireproofing Board Grade
Magnesium oxide boards (MgO boards) are manufactured by reacting magnesium chloride with magnesium oxide to form magnesium oxychloride cement. The magnesium chloride hexahydrate specification here demands extremely low iron (<0.005%) to prevent discoloration and staining. Sulfate must be minimal to avoid efflorescence on finished boards. The molar ratio of MgCl₂ to MgO is tightly controlled; any deviation from the expected purity shifts the reaction stoichiometry and compromises board strength and water resistance. A reliable supplier provides not just a COA but batch-to-batch consistency, which is non-negotiable for continuous board production lines.
Magnesium Metal Production Grade
In electrolytic magnesium smelting, anhydrous magnesium chloride or highly concentrated brine is fed into molten salt cells. The presence of water or sulfate generates impurities in the final magnesium metal and can cause dangerous cell reactions. Smelters often purchase hexahydrate flakes as the starting material, then dehydrate them under a hydrogen chloride atmosphere to produce anhydrous MgCl₂. Thus, their magnesium chloride hexahydrate specification prioritizes low sulfate, low boron, and low iron to preserve metal purity. Standard purity for this application is at least 99% MgCl₂·6H₂O.
Food Coagulant Grade
As a coagulant for tofu (nigari) or in the production of some cheeses, magnesium chloride must meet food additive regulations such as FCC (Food Chemicals Codex) or JECFA. The specification includes strict limits on heavy metals (arsenic < 3 ppm, lead < 2 ppm, mercury < 1 ppm), sulfate, and insolubles. In this market, the term “bittern” is often used, and the product may be supplied as a purified brine or flake. Buyers should request a food-grade certificate and verify that the manufacturing process excludes industrial co-products.
Uses of Magnesium Chloride Salt: Why Specifications Drive Performance
Exploring the uses of magnesium chloride salt reveals why granular specification data is so crucial. Each use case stresses a different property.
- De-icing: Leverages high solubility, hygroscopicity, and low eutectic temperature. A high-purity flake with <0.1% insolubles ensures no residue clogs storm drains or damages application equipment.
- Dust control on unpaved roads: Magnesium chloride draws moisture from the air to bind fine soil particles, reducing dust by up to 90%. A consistent chloride content and low calcium prevent crust formation that can become brittle.
- Fireproofing boards: Depends on the precise chemical reaction with MgO. Impurities like iron or manganese cause color variation; sulfate and carbonate lead to efflorescence and weakened structure. The carbonate content, in particular, must be <0.5% to avoid CO₂ release during curing.
- Magnesium metal production: The electrolytic process demands a near-anhydrous feed. Any water or hydroxyl groups in the melt produce magnesium oxide sludge, reducing current efficiency. That’s why smelters often specify a hexahydrate product with a known, low impurity profile for their own dehydration step.
- Food processing: As a tofu coagulant, magnesium chloride influences curd texture, yield, and taste. Bittern with high sulfate content can give a bitter aftertaste. A food-grade specification ensures the characteristic smooth, sweet flavor of traditional nigari tofu.
- Other niche applications: Magnesium chloride is used in refrigeration brines, cement grinding aids, and even in certain medical preparations (magnesium oil). In all cases, the application determines the acceptable impurity profile—no single magnesium chloride hexahydrate specification fits every need.
Magnesium Chloride vs Magnesium Sulfate: What’s the Difference and When to Choose Each
In industrial procurement, questions about magnesium chloride vs magnesium sulfate often arise because both are soluble magnesium salts with overlapping application areas. However, their chemistry and performance diverge sharply.
| Parameter | Magnesium Chloride (MgCl₂) | Magnesium Sulfate (MgSO₄) |
|---|---|---|
| Common hydrate | Hexahydrate (flakes) | Heptahydrate (Epsom salt) |
| Molar mass (hydrate) | 203.30 g/mol | 246.47 g/mol |
| Magnesium content | ~12% Mg by weight (hexahydrate) | ~9.9% Mg by weight (heptahydrate) |
| De-icing lowest temperature | -33°C | Not commonly used (ineffective below -5°C) |
| Soil stabilization / dust control | Excellent; hygroscopic, forms a durable crust | Less effective; dries into a powdery surface, limited hygroscopicity |
| Fireproofing board use | Key component in MgO cement | Not used; sulfate interferes with oxychloride phase formation |
| Food coagulant | Preferred for tofu (nigari) | Sometimes used but imparts bitter flavor due to sulfate |
| Agricultural supplement | Both provide magnesium; chloride may harm chloride-sensitive crops | Preferred for foliar feeding and Epsom salt applications |
For de-icing contractors, magnesium chloride vs magnesium sulfate is a straightforward decision: magnesium chloride works at far lower temperatures and resists refreezing longer. For dust control, magnesium chloride’s superior moisture retention reduces reapplication frequency. In fireproofing, magnesium sulfate is simply incompatible. Only in certain agricultural or pharmaceutical contexts might magnesium sulfate take precedence. Therefore, when sourcing for bulk industrial applications covered in this guide, magnesium chloride hexahydrate is the product of choice, and selecting the right specification ensures you capture these performance advantages.
How to Evaluate a Magnesium Chloride Hexahydrate Supplier
Your magnesium chloride hexahydrate specification is only as good as the supplier’s ability to deliver on it consistently. A one-time COA that meets specs means little if the next shipment shows a drop in purity or an unexpected increase in iron. Use this supplier evaluation framework to protect your operations:
- Certification and compliance: Does the manufacturer hold ISO 9001 certification? For food-grade material, do they have HACCP, HALAL, KOSHER, or relevant food safety certifications? Request a certificate of analysis (COA) for every batch, not just a typical specification sheet.
- Production consistency: Ask for historical data on at least 10 recent batches to verify purity variation. A reputable supplier will show a standard deviation of <0.2% on MgCl₂ content and minimal fluctuation in impurities.
- Packaging integrity: Because magnesium chloride hexahydrate is hygroscopic, packaging must include a moisture barrier—typically a polyethylene liner inside a polypropylene woven bag (25 kg, 50 kg, or 1000 kg supersacks). For ocean freight, ask about palletization and shrink-wrapping to prevent moisture ingress during transit.
- Logistics and documentation: The supplier should handle export documentation, including certificates of origin, SGS or equivalent third-party inspection, and MSDS that accurately reflect your received grade. Incoterms should match your supply chain strategy (FOB, CIF, etc.).
- Technical support: A partner, not just a vendor, will help you optimize your process with their product. Look for a supplier who can discuss your specific application and recommend the ideal physical form, particle size, and purity grade. For example, Hailei Chemical’s magnesium chloride team offers application-specific guidance for de-icing, fireproofing, and food processing.
- Sustainable and ethical practices: More buyers now require environmental compliance. Check whether the manufacturer meets local environmental regulations and whether they are certified for responsible chemical production. This is particularly important for European and North American importers.
When you have a clear magnesium chloride hexahydrate specification and a supplier that meets these evaluation criteria, you de-risk your supply chain and gain predictable process outcomes.
Common Pitfalls When Specifying Magnesium Chloride Hexahydrate
Even experienced buyers can overlook details that lead to performance gaps. Avoid these frequent mistakes:
- Assuming all hexahydrate is 46% MgCl₂: Some lower-cost products use variable hydration or contain free water. Always confirm the assay method (EDTA titration or ion chromatography) and request a moisture content test.
- Ignoring trace metal levels for color-sensitive applications: Iron as low as 50 ppm can cause pink or yellow staining in MgO boards. For white or light-colored boards, insist on < 20 ppm Fe.
- Not specifying form and particle size: Flakes, prills, and powders have different dissolution rates and handling properties. Without a defined particle size range, you might receive material that bridges in your hopper or dissolves too quickly for your spray system.
- Overlooking the need for a food-grade lot segregation: If you purchase both industrial and food-grade material from the same supplier, confirm that production lines, packaging, and warehousing are strictly segregated to prevent cross-contamination.
- Failing to test in your specific process conditions: A general specification may pass all standard tests but still underperform in your operation. Always conduct a pilot trial with a sample lot before committing to a full container load.
How Hailei Chemical Supports Your Procurement
At Weifang Hailei Fine Chemical Co., Ltd., we view a magnesium chloride hexahydrate specification not as a static document but as a dynamic quality promise. Our production lines yield hexahydrate flakes with a consistent 46% MgCl₂ content, precision-controlled impurity profiles, and a variety of packaging options tailored to your logistics needs. We serve industries from road maintenance in Scandinavia to fireproofing board plants in Southeast Asia, with full regulatory documentation and third-party testing available for every shipment.
Whether you need a bulk order of de-icing grade flakes or high-purity hexahydrate for sensitive food coagulant use, our team is ready to provide a detailed COA, samples for trial, and expert technical consultation. Visit our magnesium chloride product page for complete specifications, packaging details, and typical application data. When you’re ready to lock in competitive pricing and reliable delivery, request your customized quote and we’ll respond within one business day with a tailored solution that meets your exact specification requirements.