Confirm the hydrate before comparing physical forms
Anhydrous magnesium chloride is MgCl2 (CAS 7786-30-3), while magnesium chloride hexahydrate is MgCl2·6H2O (CAS 7791-18-6). The water in a hydrate is part of the crystal structure; it is not correctly treated as random dilution. Many commercial magnesium chloride flakes are hydrated material, but the word “flakes” does not prove the hydrate, assay or application grade.
A quotation should state the exact chemical identity, MgCl2 reporting basis, moisture or water of crystallization, physical form and guaranteed impurity limits. If one supplier reports MgCl2 on an as-received basis and another uses a dry or calculated basis, the percentages cannot be ranked until they are normalized.
| Supply form | Main procurement advantage | Main qualification risk |
|---|---|---|
| Hexahydrate flakes | Common bulk form with convenient dissolution and handling | Moisture pickup, caking, breakage and fines |
| Granules or prills | More defined particle geometry for feeding or spreading | Supplier terminology varies; sieve data are required |
| Powder | High surface area and potentially rapid dissolution | Dust, compaction, poor flow and exposure control |
| Brine or solution | Avoids on-site solid dissolution | Water freight, concentration control, tanks and corrosion |
| Anhydrous MgCl2 | Required by some water-sensitive chemical processes | Not interchangeable with hexahydrate; stringent moisture control |
Flakes are a shape, not a complete specification
Magnesium chloride flakes are often selected because they can be packed efficiently and dissolved without the dust level associated with fine powder. Their performance still depends on flake thickness, size distribution, fines, caking tendency, storage history and the design of the dissolving or spreading equipment. A photograph cannot establish those properties.
Specify an acceptable sieve distribution or an agreed visual and handling standard, plus maximum damaged or fine material where it affects the process. For long ocean routes or humid destinations, qualify the bag film, liner closure, pallet protection and container loading pattern. Magnesium chloride is hygroscopic, so packaging integrity is part of product quality rather than a separate cosmetic issue.
Granules and powder require equipment-specific trials
“Granular magnesium chloride” may refer to several size ranges. Buyers using augers, hoppers or mechanical spreaders should state the equipment and required particle window. Uniformity can help feeding, but only when the particles survive transport and do not consolidate in storage. Bulk density should be measured using an agreed method if it controls silo capacity or feeder calibration.
Powder can dissolve quickly because of its surface area, but it can also absorb moisture quickly, bridge in hoppers and generate airborne dust. A closed transfer and local exposure assessment may be needed. Do not select powder only from laboratory dissolution time if the plant cannot store and feed it consistently.
When brine is the better purchasing form
Magnesium chloride brine can be practical when the customer has liquid unloading, compatible tanks and a nearby supply route. The contract should define MgCl2 concentration, analytical method, density and temperature basis, relevant impurities and acceptable variation. Tank volume and delivered active mass must be calculated on the same basis as the supplier’s certificate.
Liquid supply transfers the work of dissolution upstream, but it also means paying freight on water. Compare delivered active MgCl2, unloading time, storage, winter operating conditions, corrosion control, spill containment and the value of reduced solids handling. A solution is not automatically cheaper or more expensive; route and plant design determine the result.
Match form and grade to the application
Deicing and dust-control buyers usually focus on application equipment, concentration, residual insolubles, corrosion management, surface compatibility and environmental requirements. Magnesium oxychloride cement or other reactive systems require a controlled chemical basis and process trial. Wastewater, textile or other industrial uses must define the contaminant or reaction target rather than assume any MgCl2 grade will work.
Consumer bath, topical, food, pharmaceutical and supplement queries represent different regulatory and documentation intents. An industrial magnesium chloride page should not claim those uses from chemical identity alone. Food-contact, pharmaceutical or personal-care suitability requires the applicable grade, manufacturing controls and current evidence for the destination market.
COA fields that make offers comparable
- Chemical identity and hydrate; CAS number where required.
- MgCl2 assay with a clearly stated reporting basis and method.
- Moisture or water-of-crystallization basis.
- Calcium, sulfate, sodium, potassium, iron or other application-relevant impurities.
- Water-insoluble matter, color or pH where the process requires them.
- Physical form, sieve distribution, fines and bulk density when handling depends on them.
- Lot number, production date, sampling plan and retained-sample procedure.
A practical form-selection sequence
- Define the application and identify whether anhydrous or hydrated chemistry is required.
- Set guaranteed chemical limits on one reporting basis.
- Select flakes, granules, powder or brine for the existing storage and dosing equipment.
- Review a representative sample and recent COA.
- Run a controlled handling and process trial with recorded conditions.
- Compare delivered active cost, handling cost, losses and supply risk.
- Put approved chemistry, form, packaging and change control into the purchase specification.
Frequently asked questions
Are magnesium chloride flakes always hexahydrate?
No. Flake is a physical description. Confirm the hydrate, CAS number, assay basis and COA.
Is powder always faster to dissolve than flakes?
Smaller particles often provide more surface area, but moisture, agglomeration, temperature, agitation and equipment design determine actual dissolution performance.
Can industrial MgCl2 be sold for bath or supplement use?
Chemical identity alone is not enough. Those uses require their own grade, manufacturing controls, documentation and destination-market compliance.
How should bulk offers be compared?
Normalize hydrate and assay basis, delivered active MgCl2, impurities, packaging, freight, handling losses, storage and verified process performance.
Technical references
Send the hydrate, MgCl2 basis, impurity limits, physical form, quantity, packing, destination and application. Review magnesium chloride supply or request a specification-based quotation.