Neodymium arsenate, also known as neodymium(III) arsenate, is the arsenate of neodymium with the chemical formula of NdAsO4. It is an inorganic compound composed of neodymium (a rare-earth lanthanide) and the arsenate anion (AsO₄³⁻). In this compound, neodymium exhibits the +3 oxidation state. It has good thermal stability, and its pKsp,c is 21.86±0.11. It is typically represented by the formula NdAsO₄ and belongs to a broader family of rare-earth arsenates.
In solid form, neodymium arsenate is usually a crystalline, insoluble material with a pale violet to pinkish appearance, reflecting the characteristic color of neodymium(III) ions. Its crystal structure is commonly similar to other rare-earth orthophosphates and arsenates, where neodymium ions are coordinated by oxygen atoms from arsenate groups.
Chemically, it is thermally stable and shows low solubility in water, but it can dissolve in strong acids. Like other arsenates, it must be handled carefully due to the toxicity of arsenic-containing compounds.
Properties
Neodymium arsenate is an inorganic compound typically represented as NdAsO₄ or in hydrated forms such as NdAsO₄·xH₂O. It appears as a crystalline solid, usually pink to violet due to the presence of neodymium(III) ions. The compound is insoluble or sparingly soluble in water but may dissolve in strong acids. Like most rare-earth arsenates, it shows high thermal stability and forms well-defined crystal lattices.
- Chemical formula: NdAsO4
- Molar mass: 313.89
- Appearance: faint pink powder
- Density: 5.3-5.9 g/cm3
- Solubility in water: insoluble
Neodymium arsenate is mainly of scientific and materials-research interest, particularly in solid-state chemistry, mineral analog studies, and investigations of rare-earth compounds. It has no widespread commercial use, but it contributes to understanding the structural and optical behavior of lanthanide materials.
Preparation
Neodymium arsenate can be obtained from the reaction between sodium arsenate (Na3AsO4) and neodymium chloride (NdCl3) in solution:
Na3AsO4 + NdCl3 → 3 NaCl + NdAsO4↓
When crystallizing from a lead pyroarsenate flux, neodymium arsenate crystals produced explode when cooled.
Neodymium arsenate also occurs in nature as a mineral, Arsenoflorencite-(Nd).
Occurrences
Neodymium arsenate does not occur abundantly as a free compound in nature. It is mainly encountered in laboratory or industrial contexts and may form as a secondary phase during the processing of neodymium-bearing minerals or arsenic-rich ores.
Applications
Its uses are primarily limited to research. Neodymium arsenate is studied in solid-state chemistry, materials science, and spectroscopy, especially for understanding rare-earth arsenate structures. It may also be used as a reference compound in analytical and crystallographic studies.
