Magnesium sulfate heptahydrate (MgSO4 7H2O) appears as white or colorless needle-like or inclined columnar crystal, being odorless, cool and slightly bitter with a molecular weight of 246.47, specific gravity 1.68, being easily soluble in water and slightly soluble in ethanol and glycerol. In 67.5 °C, it is soluble in its own crystal water. It can be subject to thermal decomposition with loss of four molecules of crystal water molecules at 70, 80 °C. It will lose all the crystalline water at 200 °C to become anhydrous product. In the air (dry), it is easy to be weathered into powder with heating gradually removing the crystal water molecules to become anhydrous magnesium sulfate. This product does not contain any toxic impurities. Magnesium sulfate heptahydrate is difficult to dissolve and thus being easier to weigh than anhydrous magnesium sulphate for being convenient for quantitative control in industry. It is mainly used for the manufacture of fertilizer, tanning, printing and dyeing, catalyst, papermaking, plastic, porcelain, pigments, matches, explosives and fireproof materials. It can be used for printing fine cotton, silk, as the weighting agent of cotton yarn and the filler of kapok products; as Epsom salt of medicine.
Agricultural application
Magnesium is the core element of chlorophyll, being able to enhance the reduction process of plants and improve the disease resistance. It is essential for photosynthesis. Magnesium is the activator of many enzymes, can promote carbohydrate metabolism, nucleic acid synthesis, phosphate conversion. Magnesium sulfate is a very important fertilizer, because it can provide the crop with rich nutrition. Magnesium can help crop growth and yield. Sulfur is the main component of proteins and enzymes in plants, which can promote root growth, enhance metabolism and redox in plants, and thus promote the growth of crops and increase the yield. Magnesium sulfate is a good fertilizer, it can not only provide magnesium and sulfur elements, and can also make the compacted soil be loose and strong, well-developed root system and enable full absorption of nutrients so that plants can become lusher. Magnesium and other 15 elements are considered to be plant growth and high-yielding nutrients. The nutritional components and fertilizers of the plants, the nutrients (nitrogen, phosphorus and potassium) contained in traditional fertilizers are clearly insufficient to increase agricultural yields while moderate nutrient (calcium, magnesium and sulfur) and micronutrients (zinc, copper, iron, manganese, boron, molybdenum and chlorine) become less in the soil, and the lack of these nutrients can result in reduced crop yields. Magnesium has been proven to be an important source of increased productivity and agricultural production, and must be replenished in a timely manner since the excessively extraction of magnesium from the soil is the major source of this widespread disease. It can be mixed with nitrogen, phosphorus and potassium into compound fertilizer or mixed fertilizer according to different needs, and can be mixed with one or more elements into various fertilizers and photosynthetic fertilizers respectively. After the contrast practical fertilization experiment of treatment of nine crops including rubber trees, fruit trees, tobacco leaves, potatoes and cereals, magnesium-containing compound fertilizer can make the crop grow 15-50% better than magnesium-free fertilizer.
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