Calcium arsenide is an inorganic compound with the chemical formula Ca2As2 and is one of the arsenides of calcium. It is a hexagonal crystal with a space group of P62m. It’s a relatively rare compound that can be synthesized through the reaction of calcium metal and arsenic in a high-temperature environment. It is isostructural with sodium peroxide and can be expressed as (Ca2+)2(As-As)4−.
Calcium arsenide is typically a dark gray or black crystalline solid. It reacts with sodium monoarsenide and silicon in a tantalum container to obtain Na4Ca2SiAs4. It reacts with potassium arsenide, iron arsenide and calcium fluoride at high temperature to obtain KCa2Fe4As4F2.
Properties
- Chemical formula: CaAs
- Molar mass: 115.00
- Appearance: It is typically a gray to black solid.
- Structure: It has a crystalline structure, where calcium and arsenic atoms are bonded in a stoichiometric ratio.
- Melting Point: Around 1,000°C (1,832°F), though exact values can vary depending on the form and purity.
- Solubility: It is insoluble in water but can react with water to release arsenine (AsH₃), a toxic gas.
- Density: Approximately 3.8 g/cm³.
- Chemical Reactivity: It is a relatively reactive compound, particularly with water. It can decompose in the presence of moisture, producing calcium hydroxide (Ca(OH)₂) and arsenic gas (AsH₃).
Natural Occurrence
It may form in small amounts in arsenic-rich mineral deposits, though it is far less abundant than other arsenic compounds like arsenopyrite or orpiment. It may also be found as part of the products of high-temperature geological processes or in association with certain types of volcanic activity where both calcium and arsenic are present in sufficient concentrations.
Synthetic Production
Calcium arsenide is primarily synthesized in laboratories and industrial settings by heating a mixture of calcium and arsenic or arsenic-containing compounds, such as arsenic trichloride (AsCl₃). It can also be produced through reactions involving calcium metal and arsenic vapors at high temperatures.
Reactivity
Calcium arsenide can react with water to produce calcium hydroxide (Ca(OH)₂) and arsine gas (AsH₃), which is highly toxic and flammable. Proper ventilation and safety protocols are essential when working with such compounds.
Uses
Calcium arsenide does not have widespread commercial applications but may be used in specific research contexts related to semiconductor materials or as a source of arsenide ions in chemical reactions.
Toxicity and Safety
Like many arsenic compounds, calcium arsenide is toxic and poses serious health risks if not handled properly. Exposure to arsenic can lead to poisoning, and it is classified as a carcinogen. Adequate precautions, such as wearing protective equipment, are necessary when working with it.
