A sulfate is a chemical compound containing the ion SO42-, or its corresponding radical. Many sulfates are found in nature as mineral deposits, including barium sulfate (BaSO4, barite), calcium sulfate (gypsum, alabaster, and selenite), and strontium sulfate (celestite).Potassium sulfate (K2SO4) and magnesium sulfate (MgSO47H2O or Epsom salts) also occur naturally. Some sulfates are produced as byproducts in other manufacturing operations. For instance, sodium sulfate is produced during battery recycling and rayon manufacturing.
Sulfates are salts or esters of sulfuric acid, H2SO4. One or both of the hydrogens are replaced with a metal or a radical (ammonium or ethyl). Sulfates that have both hydrogens replaced are known as normal sulfates. Those with only one hydrogen replaced are known as hydrogen sulfates, acid sulfates, or bisulfates. Double sulfates contain two different metals and two sulfate radicals. Organic sulfates are esters and are formed by reacting an alcohol with cold sulfuric acid or by the reaction of sulfuric acid with a double bond in an alkene. The latter reaction produces alkyl hydrogen sulfate, which can further be broken down into an alcohol by heating with water.
Most metal sulfates are soluble in water, except for barium, lead, and strontium. Calcium sulfate is only slightly soluble. Calcium sulfate exists in two forms, as anhydrite (CaSO4) and as gypsum (CaSO42H2O). Heating gypsum to 120°C forms the hemihydrate, (CaSO4)2 H2O, otherwise known as plaster of paris. Plaster of paris is widely used as a mold or model material in the metal and ceramic industries. It has also been used as a raw material in glass manufacturing.
Other sulfates are used in a variety of agricultural and industrial applications. Over half a million tons of potassium sulfate is used in the United States as fertilizer for non-grain and specialty crops like tobacco. Ammonium sulfate ((NH4)2 SO4) is also used as a fertilizer, in addition as an ingredient to prepare other ammonium compounds and for fireproofing. Sodium sulfate or salt cake (Na2SO4) is used to make detergents, textiles and paper (for the bleaching process). Magnesium sulfate is also used in the paper and fertilizer industries.
Many sulfates are used in the ceramic or glass industries. Strontium sulfate is sometimes used to produce iridescence in glass and pottery glazes, and can also be used as a fining agent (to remove bubbles in the molten glass) in crystal glass. Sodium sulfate is also used as a fining agent. Barium sulfate can be used in the manufacture of porcelain enamels, to reduce dimpling defects or to improve workability. Magnesium sulfate is also used in the manufacture of enamels.Cobalt sulfate (CoSO47H2O) is used as a blue colorant in ceramics, ferrous sulfate (FeSO47H2 O) as a red colorant, and copper sulfate (CuSO45H2O is sometimes used to make ruby glass.
This is the complete article, containing 452 words
(approx. 2 pages at 300 words per page).
