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7487-88-9
futurechemical
7487-88-9
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Molecular formula | MgSO₄·7H₂O (heptahydrate, most common) / MgSO₄ (anhydrous) |
CAS number | 10034-99-8 (heptahydrate), 7487-88-9 (anhydrous) |
Appearance | Heptahydrate: Colorless needle-like or columnar crystals (like sugar); Anhydrous: White powder |
Solubility | Very soluble in water – solubility of the heptahydrate is 71 g/100 mL at 25°C. |
smell | Its extremely strong bitter and salty taste—hence the name "Sulfur Salt" or "Epsom Salt"—is derived from this. |
Magnesium content | Approximately 9.9% (heptahydrate, calculated as Mg) |
Magnesium is the central atom of chlorophyll molecules—without magnesium, photosynthesis is like a car without an engine. In many parts of the world, the magnesium content of soil has declined due to long-term farming and improper fertilization—especially in sandy and acidic soils, where magnesium is severely leached away.
Magnesium-deficient crops
All crops
Yellowing between veins in older leaves – because magnesium is mobile within the plant, when magnesium is deficient, magnesium in older leaves is transported to newer leaves – older leaves turn yellow first;
potato
Tuber yield decreased significantly – magnesium is directly involved in the transport of photosynthetic products (starch) from leaves to tubers;
grapes and tomatoes
Fruit sugar content decreases – sugar is synthesized in the leaves, and leaves deficient in magnesium have poor “production efficiency”.
Magnesium sulfate fertilization method
Way | operate |
Soil base application | Mix with nitrogen, phosphorus, and potassium fertilizers – 5-15 kg MgSO₄·7H₂O/mu |
Foliar spraying | 1%~2% MgSO₄ solution—the fastest way to correct magnesium deficiency. |
hydroponic nutrient solution | Magnesium sulfate is the standard source of magnesium and sulfur in all hydroponic formulations—the core of component B in A/B solutions. |
Consistent with the logic discussed in the food section, magnesium is an essential element for all animals. Magnesium sulfate is used as a magnesium source in feed. Especially for ruminants—where the magnesium content in tender grass in spring pastures is extremely low—extra supplementation is needed to prevent hypomagnesemia ("green grass convulsions"—described in detail in the previous section on magnesium lactate).
Magnesium sulfate is the cheapest and most readily available soluble magnesium salt in industry.
Leather making: In the chrome tanning process, it helps the chrome tanning agent penetrate the leather fibers evenly—while also acting as a filler to increase the fullness of the leather;
Dyeing and Printing: In the dyeing of cotton fabrics with reactive dyes, sulfuric acid is used as an alkali and magnesium sulfate as a...
Alkali-absorbing and dyeing retarder
Mg²⁺ competes with dyes for negative charge sites on the fiber, slowing down the dye uptake rate and preventing "color spots"—resulting in more even dyeing.
Papermaking: Used as a processing aid in the production of certain specialty papers.
Magnesium sulfate is mainly used in building materials, primarily in sorel cement systems and fire-resistant boards.
Magnesium oxychloride cement is an air-hardening cementitious material made by mixing active MgO with MgCl₂ solution. It has high flexural strength, fast hardening, and good adhesion to wood fibers—and is used to manufacture lightweight fireproof partition boards, fireproof door core boards, and exterior wall insulation boards. Magnesium sulfate is used as a modifying additive in this system—partially replacing MgCl₂ to reduce moisture absorption, efflorescence, and warping deformation in the product.
Magnesium sulfate itself is also a filler component in some flame-retardant boards—it decomposes and releases water of crystallization when heated (absorbing heat and cooling down)—playing an auxiliary role in flame retardancy.
In industrial water treatment, magnesium sulfate is used as a magnesium source for:
Cooling water systems – trace amounts of magnesium ions help inhibit corrosion and scale buildup;
Urban water supply – In some areas with low-magnesium soft water, magnesium is supplemented in the water supply to improve residents' magnesium intake.
Industrial wastewater treatment – used as an auxiliary precipitant in the treatment of certain phosphorus- and fluoride-containing wastewater.
In addition to basic bath salts, magnesium sulfate also appears in:
Foot bath salts – relieve foot fatigue;
Body scrub – MgSO₄ crystals act as gentle physical exfoliating particles;
Some shampoos and conditioners act as volume enhancers and texture modifiers.
Lead-acid batteries: Adding magnesium sulfate to the electrolyte improves battery cycle life;
Ceramics: fluxes and magnesium sources in glazes and bodies.
Magnesium sulfate is the most typical "universal inorganic salt"—the same MgSO₄ molecule has traversed all dimensions of human life, from saving lives to relaxing baths, from green leaves to tofu, from leather to fireproof boards.
