Magnesium Sulfate Heptahydrate CAS 10034-99-8、 Magnesium Sulfate Anhydrous CAS 7487-88-9、Magnesium Sulfate Monohydrate CAS 14168-73-1

Magnesium Sulfate Manufacturer — Heptahydrate, Monohydrate & Anhydrous Grades 

Magnesium Sulfate isn't a single product — it's a compound that ships in three distinct hydrate forms. Whether you know it as Magnesium Sulfate, Magnesium Sulphate, Epsom Salt, or Kieserite, the formula is MgSO4, and the version you actually need depends entirely on your application. This page covers all three forms — Heptahydrate, Monohydrate, and Anhydrous — so you can confirm the right one before you request a quote.

If you're specifically looking for a chloride-based magnesium source instead — for de-icing, dust control, or drilling fluid applications — that's a different compound with different sourcing logic; see our Anhydrous Magnesium Chloride page rather than this one.

Which hydrate form do you need? 

• Magnesium Sulfate Heptahydrate (Epsom Salt, CAS 10034-99-8, MgSO4·7H2O) — roughly 51% crystal water. Best fit: bath and cosmetic salts, straight soil topdressing, quick-release foliar spray, and any application where fast solubility matters more than storage stability.

• Magnesium Sulfate Monohydrate (Kieserite, CAS 14168-73-1, MgSO4·H2O) — roughly 13% crystal water. Best fit: granular NPK compound fertilizer, feed-grade mineral premix, and industrial dry-mix formulations where low, stable moisture content prevents caking and keeps blending lines running clean.

• Anhydrous Magnesium Sulfate (CAS 7487-88-9, MgSO4) — essentially no crystal water, highest Mg density per ton. Best fit: applications needing maximum magnesium content per unit weight, or as a feedstock to rehydrate into monohydrate or heptahydrate downstream.

The three forms are chemically the same salt at different hydration states, and they're genuinely interchangeable in terms of raw magnesium and sulfur content — what differs is moisture behavior, solubility speed, and how they perform in your specific process. If you're not sure which one fits, tell us your application and we'll confirm rather than leave you guessing from a spec sheet.

How the three forms relate to each other in production

Magnesium Sulfate Heptahydrate is the naturally crystallized form. Magnesium Sulfate Monohydrate is produced by controlled dehydration of the heptahydrate under heat, driving off crystal water until the compound stabilizes at roughly 13% moisture. Anhydrous Magnesium Sulfate takes that process further, removing essentially all crystal water. Because monohydrate and anhydrous are both derived from heptahydrate through drying, the consistency of that drying process directly affects free-moisture uniformity batch to batch — which is exactly the variable that matters most if you're running an automated granulation or premix line. This is also why we test free moisture on every batch rather than relying on a single spec sheet across all shipments and grades.

Magnesium Sulfate Heptahydrate 

Also known as Epsom Salt, this is the form most people are familiar with. Applications include:

• Agriculture: straight magnesium-sulfur fertilizer, foliar spray, soil topdressing where fast solubility is the priority

• Cosmetic & Personal Care: bath salts, exfoliants, topical soaks

• Food: minor use as a firming agent and nutrient supplement in select formulations

Magnesium Sulfate Monohydrate

Also known internationally as Kieserite, this is the low-moisture form preferred wherever caking and storage stability are process concerns.

• Fertilizer & Agriculture: blending component in NPK compound fertilizers and water-soluble fertilizers, where low moisture keeps granulation lines running clean

• Animal Feed: magnesium and sulfur source in mineral premixes, where consistent particle size and low free-moisture are required for premix stability

• Industrial Use: raw material in paper sizing, textile dyeing auxiliaries, glass and ceramics processing

Anhydrous Magnesium Sulfate 

The fully dehydrated form, valued where magnesium density per shipped ton is the deciding factor, or as a chemical intermediate.

• Industrial & Chemical: desiccant applications, chemical synthesis intermediate, feedstock for producing monohydrate or heptahydrate downstream

• Pharmaceutical & Reagent Use: analytical and reagent-grade applications specifying a defined anhydrous input

Packaging & logistics

Standard packing across all three forms: 25kg or 50kg PP woven bags with PE liner, or 500kg/1000kg jumbo bags for bulk buyers loading by container or truck. Neutral packing and customized labeling are available for private-label and distributor accounts. Anhydrous and monohydrate forms should be stored sealed and away from moisture exposure to maintain their low-hydrate state; heptahydrate is more tolerant of ambient humidity but should still be kept dry to prevent clumping.

Why source your Magnesium Sulfate through us

Procurement teams buying inorganic salts by the ton are usually solving for three things at once, regardless of which hydrate form they land on: consistent quality batch to batch, a supplier who can confirm the right hydrate for their process without a guessing game, and pricing that survives a full sourcing comparison. That's the specific gap we work in — batch-tested COAs on every shipment across all three forms, flexible order volumes that scale from trial quantities to full container loads, and direct sourcing relationships that keep pricing competitive without cutting corners on purity. If you've been burned before by a supplier who quoted well and then shipped inconsistent quality, that's exactly the risk we're set up to remove.

Frequently asked questions

Q:What's the difference between Magnesium Sulfate Heptahydrate, Monohydrate, and Anhydrous? 

A:They're the same salt (MgSO4) at three different hydration levels. Heptahydrate carries the most crystal water and dissolves fastest, monohydrate carries the least practical water content while staying non-hygroscopic and stable, and anhydrous carries none but is hygroscopic and needs sealed handling. The right one depends on whether your priority is fast solubility, storage stability, or maximum magnesium density.

Q:Is Epsom Salt the same thing as Magnesium Sulfate? 

A:Epsom Salt specifically refers to the heptahydrate form. "Magnesium Sulfate" on its own is often used loosely to mean any of the three hydrates, so when you see it used generically, confirm which hydrate is actually being quoted.

Q:Can I substitute one hydrate form for another in my process? 

A:Not directly without adjusting your formulation — the three forms have different weight percentages of active MgSO4 per unit mass, so dosing rates need to be recalculated if you switch forms. We can help with that conversion if you're evaluating a switch.

Q:What's your minimum order quantity? 

A:MOQ is flexible depending on grade, hydrate form, and packing — sample quantities are available for quality verification before you commit to a bulk order.

Q:Do you provide a Certificate of Analysis? 

A:Yes, every batch across all three forms ships with a COA, and third-party testing can be arranged on request.

Get a quote

Tell us your target hydrate form (heptahydrate, monohydrate, or anhydrous), grade, volume, and destination port, and we'll come back with a specification sheet, COA sample, and pricing — usually within one business day.

Application

To be used in fertilizer、feed additive、food & beverage and industrial uses.