Cobalt(II) chloride

Cobalt(II) chloride is an inorganic salt composed of cobalt(II) cations and chloride anions, with formula CoCl₂. It occurs in anhydrous and hydrated forms whose colors and structures differ.

Cobalt: Cobalt is a chemical element with atomic number 27 and symbol Co. Cobalt(II) chloride contains cobalt in its +2 oxidation state.
Coordination complex: A coordination complex has a central metal atom or ion bonded to surrounding ligands. Cobalt ions bind water or chloride ligands in solution and hydrated solids.
Humidity indicator: A humidity indicator is a material whose visible state changes in response to moisture in its surroundings. Cobalt chloride has been used to indicate moisture through hydration-related color changes.
Cobalt toxicity: Cobalt toxicity is harm caused by excessive exposure to cobalt or its compounds. Cobalt(II) chloride presents health hazards through inhalation, ingestion, or skin exposure.
Chloride: Chloride is the negatively charged ion Cl⁻, formed when chlorine gains an electron. Two chloride ions balance each cobalt(II) ion in the salt.
Ligand field theory: Ligand field theory describes how surrounding ligands split the energies of a transition-metal ion’s d orbitals. Changes in cobalt’s coordination environment alter the light it absorbs.
Silica gel: Silica gel is a porous, amorphous form of silicon dioxide used chiefly as a desiccant and adsorbent. Cobalt chloride indicators have been combined with silica gel to show desiccant saturation.
Carcinogen: A carcinogen is an agent capable of causing cancer in humans or other organisms. Cobalt(II) chloride is classified as a suspected carcinogen by major hazard systems.
Ionic compound: An ionic compound consists of cations and anions held together by electrostatic attraction. The salt’s formula expresses the charge-balanced ratio of its ions.
Hydration: Hydration is the association of water molecules with ions or molecules, often in solution. Water coordinates cobalt ions and produces hydrated forms with distinct colors.

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