Is Industrial Magnesium Chloride Flake Hydrated Magnesium Sulfate?

A customer has asked us whether industrial magnesium chloride flake is hydrated magnesium sulfate. The answer is no—they are completely different substances.

Industrial magnesium chloride flake (magnesium chloride hexahydrate) and hydrated magnesium sulfate (mainly magnesium sulfate heptahydrate) have very distinct differences in chemical composition, appearance, color, and texture:

I. Chemical Composition

· Magnesium chloride flake: Main component is magnesium chloride (MgCl₂), usually with crystal water, known as magnesium chloride hexahydrate.

· Magnesium sulfate: Chemical formula is MgSO₄ (e.g., Epsom salt, magnesium sulfate heptahydrate).

They share the same cation but have completely different anions, with distinct properties, applications, and safety profiles.

· Magnesium chloride flake: MgCl₂·6H₂O

· Magnesium sulfate: MgSO₄·7H₂O (and other hydrates)

1. Industrial Magnesium Chloride Flake (MgCl₂·6H₂O)

· Form: Flaky, thin-sheeted or fragmented. Irregular thin flakes and fragments with uneven edges; not granular or powdery.

· Color:

o Industrial grade: Yellowish-brown, tawny, or grayish-white (due to impurities)

o Refined white grade: White or milky white

· Texture: Brittle and fragile; extremely hygroscopic. It quickly absorbs moisture, becomes soft and sticky, and may even dissolve when exposed to air.

2. Hydrated Magnesium Sulfate (MgSO₄·7H₂O, Magnesium Sulfate Heptahydrate)

· Form: Acicular, oblique columnar, or fine granular. Slender crystals resembling needles or small columns; not flaky.

· Color: Pure white, colorless and transparent. Industrial grade is usually bright white fine crystals with almost no impurities.

· Texture: Dry, loose, and free-flowing. Stable in air and not prone to caking (will slowly effloresce in dry conditions).

Core Comparison Table

Summary

Magnesium chloride flake is thin and flaky, yellowish-brown in color, and becomes sticky when touched.Magnesium sulfate is needle-like or fine granular, snow-white, and dry to the touch.

Although the two are used in similar fields such as aquaculture and agriculture, they are not interchangeable.