zinc sulfate, chemical compound ZnSO₄, a very water soluble, transparent, colorless, crystalline compound. It is commonly used as the heptahydrate, ZnSO₄·7H₂O, and is commonly called white vitriol; it occurs naturally as the mineral goslarite, and can be prepared by reacting zinc with sulfuric acid. It is used to supply zinc in animal feeds, fertilizers, and agricultural sprays; in making lithopone; in coagulation baths for rayon; in electrolyte for zinc plating; as a mordant in dyeing; as a preservative for skins and leather; and in medicine as an astringent and emitic.

sulfate, chemical compound containing the sulfate (SO₄) radical. Sulfates are salts or esters of sulfuric acid, H₂SO₄, formed by replacing one or both of the hydrogens with a metal (e.g., sodium) or a radical (e.g., ammonium or ethyl). Sulfates in which both hydrogens are replaced are called normal sulfates; sulfates in which only one hydrogen is replaced are called hydrogen sulfates, acid sulfates, or bisulfates. Most metal sulfates are readily soluble in water, but calcium and mercuric sulfates are only slightly soluble, while barium, lead, strontium, and mercurous sulfates are insoluble. In chemical analysis, the sulfate ion, SO₄^-2, is usually detected by adding barium chloride solution; the white barium sulfate precipitate that forms is insoluble in hydrochloric acid. Sulfates are widely distributed in nature. Barium sulfate occurs as barite; calcium sulfate is found as gypsum, alabaster, and selenite; Epsom salts is magnesium sulfate; sodium sulfate occurs as its decahydrate, Glauber's salt; and strontium sulfate occurs as celestite. Some sulfates were formerly known as vitriols; blue vitriol is cupric sulfate, green vitriol is ferrous sulfate, and white vitriol is zinc sulfate. Alums are double sulfates, containing two different metals and two sulfate radicals. Organic sulfates are esters. They can be formed by reacting an alcohol with cold sulfuric acid. They are also formed by the reaction of sulfuric acid with a double bond in an alkene; the product is called an alkyl hydrogen sulfate. An alkyl hydrogen sulfate can be broken down to an alcohol and sulfuric acid by heating it with water (hydrolysis); this reaction is often used to synthesize alcohols. Sulfates play a significant role both in the chemical industry and in biological systems. Sulfuric acid is used in lead storage batteries and in the manufacture of nitric acid; copper sulfate is a common algicide. Organisms found near deep-sea thermal vents use sulfates for energy in place of sunlight.

sodium sulfate, chemical compound, Na₂SO₄. It is a white, orthorhombic crystalline compound at ordinary temperatures; above 100°C; it assumes a monoclinic structure, and above about 250°C; it assumes a hexagonal structure. Sodium sulfate is soluble in cold water and very soluble in hot water. It forms two hydrates; the decahydrate is Glauber's salt. Anhydrous sodium sulfate is found in nature as the mineral thenardite. The major commercial source of sodium sulfate is salt cake, a byproduct of the production of hydrochloric acid from sodium chloride (common salt) by treatment with sulfuric acid. It is obtained (with other chemicals) by evaporation of natural brines. It is also obtained as a byproduct of viscose rayon manufacture and in several other, less important ways. The principal use of sodium sulfate is in processing wood pulp for making kraft paper. It is also used in glass manufacture, textile dyeing, and synthetic detergents.

ferrous sulfate or iron (II) sulfate, chemical compound, FeSO₄. It is known as the monohydrate, FeSO₄·H₂O; the tetrahydrate, FeSO₄·4H₂O; the pentahydrate, FeSO₄·5H₂O; and the heptahydrate, FeSO₄·7H₂O. The heptahydrate is also called green vitriol, copperas, or melanterite (a mineral that commonly occurs with pyrite). It is a blue-green monoclinic crystalline water-soluble salt. It is prepared commercially by oxidation of pyrite (iron sulfide) or by treating iron with sulfuric acid. It is used in the manufacture of inks, in wool dyeing as a mordant, and in water purification as a substitute for aluminum sulfate. It melts at 64°C;, and at 90°C; it loses water of hydration to form the monohydrate, a white, monoclinic, crystalline powder that occurs naturally as the mineral szomolnokite. The mineral siderotil is iron sulfate pentahydrate.

ferric sulfate or iron (III) sulfate, chemical compound, Fe₂(SO₄)₃, a yellow rhombic crystalline hygroscopic water-soluble salt that decomposes when heated to a temperature of 480°C;. The enneahydrate, Fe₂(SO₄)₃·9H₂O, is a deliquescent rhombic crystalline salt that occurs in nature as the mineral coquimbite. It is used as a mordant in dyeing, as a coagulant for industrial wastes, in pickling baths for aluminum and steel, and in pigments.

cupric sulfate or copper (II) sulfate, chemical compound, CuSO₄, taking the form of white rhombohedral crystals or amorphous powder. It decomposes at 650°C; to cupric oxide (CuO). It is fairly soluble in water and when dissolved forms the pentahydrate, CuSO₄·5H₂O, the form that is most familiar. The pentahydrate can be collected as blue triclinic crystals; it is also known as blue vitriol. It loses part of its water of crystallization when heated to 110°C; and fully dehydrates at 150°C;. Cupric sulfate is used in copperplating, in dyeing (as a mordant), in wet-cell batteries, in pigments, and in insecticides, fungicides, and algicides. It is insoluble in alkali solutions, a property used in the preparation of Bordeaux mixture; lime (calcium hydroxide) is added to moist cupric sulfate, forming a basic cupric sulfate precipitate (a mixture of cupric sulfate and cupric hydroxide). The anhydrous sulfate is used to detect the presence of water in certain organic liquids; it turns into the blue pentahydrate, e.g., when added to alcohol that contains water. Cupric sulfate is prepared by the action of warm dilute sulfuric acid (oil of vitriol) on copper metal or cupric oxide; it is also a byproduct of copper sulfide ore refining. It occurs naturally in the minerals chalcanthite (the pentahydrate), hydrocyanite (the anhydrous sulfate), and brochantite (a basic sulfate, CuSO₄·3Cu(OH)₂).

copper sulfate, common name for the blue crystalline heptahydrate of cupric sulfate, in which copper has valence +2. It may also refer to cuprous sulfate (Cu₂SO₄), in which copper has valence +1.

barium sulfate: see barite.

ammonium sulfate, chemical compound, (NH₄)₂SO₄, a colorless-to-gray, rhombohedral crystalline substance that occurs in nature as the mineral mascagnite. It is soluble in water and insoluble in alcohol or liquid ammonia. It is prepared commercially by passing ammonia, obtained from destructive distillation of coal, into sulfuric acid and is used as a fertilizer, in preparing other ammonium compounds, and for fireproofing.

Any of numerous inorganic and organic chemical compounds related to sulfuric acid (H₂SO₄). One subgroup comprises salts containing the sulfate ion (SO₄²⁻) linked via ionic bonds with any of various cations. Another subgroup of sulfates, the esters, are organic compounds in which sulfuric acid's hydrogen atoms are replaced by organic groups (e.g., methyl, ethyl, phenyl); a carbon atom in the organic group bonds to an oxygen atom, whose second bond is to the sulfur atom. (In sulfonates, a carbon atom bonds directly to the sulfur atom.) Seealso bonding.

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or oil of vitriol

Dense, colourless, oily, corrosive liquid inorganic compound (H₂SO₄). A very strong acid, it forms ions of hydrogen or hydronium (H⁺ or H₃O⁺), hydrogen sulfate (HSO₄⁻), and sulfate (SO₄²⁻). It is also an oxidizing (see oxidation-reduction) and dehydrating agent and chars many organic materials. It is one of the most important industrial chemicals, used in various concentrations in manufacturing fertilizers, pigments, dyes, drugs, explosives, detergents, and inorganic salts and acids, in petroleum refining and metallurgical processes, and as the acid in lead-acid storage batteries. It is made industrially by dissolving sulfur trioxide (SO₃) in water, sometimes beyond the saturation point to make oleum (fuming sulfuric acid), used to make certain organic chemicals.

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