Sulfaadid

Sulfates, or sulfaadid in Estonian, are a class of chemical compounds containing the sulfate group, SO4^2−, or related sulfate esters. They occur as inorganic salts of various cations and as sulfate esters in organic chemistry. The sulfate group is tetrahedral with sulfur in the +6 oxidation state; the anion is stabilized by resonance among the four oxygens, giving it a −2 charge and high polarity.

Sulfates form salts with many metals, such as sodium sulfate (Na2SO4), calcium sulfate (CaSO4), and barium sulfate (BaSO4). Solubility varies: most alkali metal sulfates are water-soluble; BaSO4 is practically insoluble, and calcium sulfate is sparingly soluble. Natural minerals include gypsum (CaSO4·2H2O), anhydrite (CaSO4), and baryte (BaSO4).

Industrial production is tied to sulfuric acid chemistry: sulfates arise from neutralization of acids, flue gas desulfurization by products, and mining of sulfate minerals. Sulfate esters in organic chemistry, such as alkyl or aryl sulfonates, are common in detergents and pharmaceuticals.

Applications: gypsum and plaster are used in building materials; calcium sulfate is used in cement and drywall; sodium sulfate serves as a drying agent and in pulp and textile processes; various metal sulfates are used as reagents, pigments, or in fertilizers. Sulfate esters are widely used as surfactants and excipients.

Safety and environment: sulfates are typically low in toxicity, but concentrated sulfuric acid and some metal sulfates can be corrosive or harmful. Elevated sulfate levels in water can affect aquatic life and drinking-water quality; regulatory limits apply to industrial discharges.