Bismuth(III) iodide

Bismuth(III) iodide

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Names
IUPAC name Bismuth(III) iodide
Other names Bismuth iodide, bismuth triiodide
Identifiers
CAS Number	7787-64-6
ChemSpider	21172753
Jmol 3D model	Interactive image
PubChem	111042
InChI InChI=1/Bi.3HI.3H/h;3*1H;;;/q+3;;;;;;/p-3/rBiH3.3HI/h1H3;3*1H/q+3;;;/p-3 Key: HXTWPIJUKIDKIH-ZPTXHWADAA
SMILES [I-].[I-].[I-].[BiH3+3]
Properties
Chemical formula	BiI3
Molar mass	589.69 g/mol
Appearance	greenish-black crystals
Density	5.778 g/cm3
Melting point	408.6 °C (767.5 °F; 681.8 K)
Boiling point	542 °C (1,008 °F; 815 K)
Solubility in water	0.7761 mg/100 mL (20 °C)
Solubility	50 g/100 mL ethanol 50 g/100 mL 2M hydrochloric acid
Structure
Crystal structure	Trigonal, hR24
Space group	R-3, No. 148
Vapor pressure	{{{value}}}
Related compounds
Other anions	Bismuth(III) fluoride Bismuth(III) chloride Bismuth(III) bromide
Other cations	Nitrogen triiodide Phosphorus triiodide Antimony triiodide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Bismuth(III) iodide is the inorganic compound with the formula BiI₃. This gray-black solid is the product of the reaction of bismuth and iodine, which once was of interest in qualitative inorganic analysis.

Bismuth(III) iodide adopts a distinctive crystal structure, with iodide centres occupying a hexagonally closest-packed lattice, and bismuth centres occupying either none or two-thirds of the octahedral holes (alternating by layer), therefore it is said to occupy one third of the total octahedral holes.

Synthesis

Bismuth(III) iodide forms upon heating an intimate mixture of iodine and bismuth powder:

2Bi + 3I₂ → 2BiI₃

BiI₃ can also be made by the reaction of bismuth oxide with aqueous hydroiodic acid:

Bi₂O₃(s) + 6HI(aq) → 2BiI₃(s) + 3H₂O(l)

Reactions

Since bismuth(III) iodide is insoluble in water, an aqueous solution can be tested for the presence of Bi³⁺ ions by adding a source of iodide such as potassium iodide. A black precipitate of bismuth(III) iodide indicates a positive test.

Bismuth(III) iodide forms iodobismuth(III) anions when heated with halide donors:

2 NaI + BiI₃ → Na₂[BiI₅]