Calciates

Calciates are chemical compounds that contain the calcium cation, Ca2+, paired with various anions. In common usage, the term refers to calcium salts—calcium-based compounds formed when calcium ions react with anions such as carbonate, sulfate, phosphate, nitrate, or organic carboxylates. Calciates are typically crystalline solids with relatively high lattice energy; their solubility in water varies widely depending on the accompanying anion.

Common examples include calcium carbonate (CaCO3), calcium sulfate (CaSO4), calcium phosphate (Ca3(PO4)2), calcium nitrate (Ca(NO3)2), calcium chloride (CaCl2), and calcium oxalate (CaC2O4). Organic calciates such as calcium citrate or calcium lactate are also widely used as dietary supplements. Many calciates are sparingly soluble at neutral pH (for instance, CaCO3 and Ca3(PO4)2), while others dissolve more readily (such as CaCl2 or Ca(NO3)2). Solubility is influenced by temperature and pH and by the specific anion involved.

Occurrence and significance: calciates occur naturally as minerals, including calcite (CaCO3), aragonite, gypsum (CaSO4·2H2O), and various calcium phosphates. They play essential roles in geology, soil chemistry, and biology. In living organisms, calcium salts contribute to skeletal material (for example, hydroxyapatite in bone and dental enamel) and participate in signaling and buffering processes.

Applications: calciates have broad uses in industry, construction, agriculture, food, and medicine. They include lime production from CaCO3, cement and plaster formation, water treatment, and dietary supplements such as calcium gluconate, calcium citrate, and calcium lactate.