Potassium Sulfate (redirected from Sulfate of potash)

potassium sulfate [pə′tas·ē·əm ′səl‚fāt]

(inorganic chemistry)

K₂SO₄Colorless crystals with bitter taste; soluble in water, insoluble in alcohol; melts at 1072°C; used as an analytical reagent, medicine, and fertilizer, and in aluminum and glass manufacture. Also known as salt of Lemery.

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Potassium Sulfate 

a salt; colorless crystals. Density, 2.66 g/cm³, melting point, 1074°C. Solubility, 11.1 g per 100 g H₂O at 20°C (24.1 g at 100°C).

Potassium sulfate is a consituent of natural potassium salts, such as schoenite (K₂SO₄·MgS0₄·6H₂O), from which it is also extracted. Potassium sulfate is used in the preparation of alum and potash. In agriculture, it serves as a concentrated chlorine-free potassium fertilizer, containing no less than 45–52 percent K₂O, no more than 1 percent MgO, and no more than 10 percent moisture; it is applied primarily to the soil under chlorine-sensitive crops (potatoes, tobacco, flax, grapes, citrus fruits). The presence of the sulfate ion in the fertilizer has a favorable effect on the yield of crucifers (cabbage, rutabagas, turnips) and legumes, which require a large amount of sulfur.

Heating potassium sulfate with concentrated sulfuric acid forms the acid salt potassium hydrosulfate (bisulfate): K₂SO₄ + H₂SO₄ = 2KHS0₄. At temperatures above its melting point (210°C), potassium hydrosulfate is converted first to potassium pyrosulfate (2KHS0₄ = K₂S₂0₇ + H₂0) and then to potassium sulfate and sulfuric anhydride (K₂S₂O₇ = K₂SO₄ + SO³). This reaction is used for converting substances that are nearly insoluble in acids (for example, calcinated A1₂O₃, Fe₂O₃, Cr0₃) into soluble sulfates. Potassium hydrosulfate is also used as a flux in metallurgy.