7778-80-5

Potassium sulfate, sulfate of potash, K2SO4, white solid, soluble. Common constituent of potassium salt minerals.

Potassium sulfate,K2804, also known as salt of Lemery and arcanite, is a colorless crystalline solid that melts at 1072°C(1960 OF). It is soluble in water,but insoluble in alcohol. Potassium sulfate is used in manufacturing glass, aluminum, fertilizers, and in medicine.

Colorless or white crystals or white granules or powder; rhombohedral structure; bitter taste; density 2.66 g/cm³; melts at 1,069°C; vaporizes at 1,689°C; moderately soluble in water, 12 g/100mL at 25°C and 24g/100mL at 100°C; slightly soluble in glycerol; insoluble in alcohol, acetone, and carbon disulfide.

Potassium and sodium sulfates and their double sulfates with calcium and magnesium occur naturally in various salt lakes. Potassium sulfate also occurs in certain volcanic lava. Its double salt with magnesium occurs in nature, as the mineral langbeinite.
Potassium sulfate is used in fertilizers as a source of potassium and sulfur, both of which are essential elements for plant growth. Either in sim-ple form or as a double salt with magnesium sulfate, potassium sulfate is one of the most widely consumed potassium salts in agricultural applications. It is preferred over potassium chloride for certain types of crops; such as, tobac-co, citrus, and other chloride-sensitive crops. Some other applications include making gypsum cements; to make potassium alum; in the analysis of Kjeldahl nitrogen; and in medicine.

A white crystallinepowder, K₂SO₄, soluble inwater and insoluble in ethanol;rhombic or hexagonal; r.d. 2.66; m.p.1069°C. It occurs naturally assch?nite (Strassfurt deposits) and inlake brines, from which it is separatedby fractional crystallization. Ithas also been produced by the Hargreavesprocess, which involves theoxidation of potassium chloride withsulphuric acid. In the laboratory itmay be obtained by the reaction ofeither potassium hydroxide or potassiumcarbonate with sulphuric acid.Potassium sulphate is used in cements,in glass manufacture, as afood additive, and as a fertilizer(source of K⁺) for chloride-sensitiveplants, such as tobacco and citrus.

Potassium sulfate is produced by various methods, selection of process depending on availability and cost of raw materials.
The salt may be obtained from its naturally occurring mineral, langbeinite,K₂SO₄?2MgSO₄. The ore first is crushed and washed with water to separate sodium chloride. After that, magnetite is separated from the washed langbei-nite by magnetic separation. After the separation of these two major impuri-ties, the purified double salt is treated with an aqueous solution of potassium chloride to obtain potassium sulfate:
K₂SO₄?2MgSO₄ + 4KCl →3K₂SO₄+ 2MgCl₂
The solution is filtered to remove insoluble residues and the products are separated from their aqueous mixture by crystallization.
Potassium sulfate also is produced from the mineral kieserite, MgSO4?H₂O by treatment with potassium chloride. The intermediate double salt obtained reacts further with potassium chloride to form potassium sulfate:MgSO₄?H₂O + 2KCl + 4H₂O →K₂SO₄?MgSO₄?6H₂O + MgCl₂
K₂SO₄?MgSO₄?6H₂O + 2KCl →2K₂SO₄+ MgCl₂
Potassium sulfate is separated from the more soluble magnesium chloride by crystallization.
Also, potassium sulfate can be made by two other processes in which no naturally occurring mineral is employed. In the Mannheim process, the salt is produced by action of sulfuric acid on potassium chloride:2KCl + H₂SO₄→K₂SO₄+ 2HCl
In Hargreaves process, which is a slight variation of the Mannheim method, potassium sulfate is made by heating a mixture of potassium chlo-ride, sulfur dioxide, air and water:4KCl + 2SO₂+ 2H₂O + o₂→2K₂SO₄+ 4HCl.

Nonflammable

Potassium sulfate [7778-80-5] M 174.3, m 1069o, d 4 2.67 It crystallised from distilled water (4mL/g at 20o; 8mL/g at 100o) between 100o and 0o.