Potassium tetraiodomercurate(II)
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| Names | |
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| IUPAC name
potassium tetraiodidomercurate(II)
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| Other names
potassium mercuric iodide,
Nessler's reagent (principal component) | |
| Identifiers | |
3D model (JSmol)
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| ChEBI | |
| ChemSpider | |
| ECHA InfoCard | 100.029.082 |
| EC Number |
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PubChem CID
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| UN number | 3287 |
CompTox Dashboard (EPA)
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| Properties | |
| K2[HgI4][1] | |
| Appearance | yellow crystals |
| Odor | odorless |
| Density | 4.29 g/cm3 |
| very soluble | |
| Solubility | soluble in alcohol, ether, acetone |
| Hazards | |
| Safety data sheet (SDS) | External MSDS for Nessler's reagent |
| Related compounds | |
Other anions
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Mercury(II) iodide |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Potassium tetraiodomercurate(II) is an inorganic compound consisting of potassium cations and the tetraiodomercurate(II) anion. It is mainly used as Nessler's reagent, a 0.09 mol/L solution of potassium tetraiodomercurate(II) (K2[HgI4]) in 2.5 mol/L potassium hydroxide, used to detect ammonia.[2]
Preparation and structure
Crystallizing from a concentrated aqueous solution of mercuric iodide with potassium iodide is the monohydrate KHgI3.H2O, which is pale orange.[3] In aqueous solution this triodido complex adds iodide to give the tetrahedral tetraiodo dianion.[4]
Solutions of K2HgI4 react with Cu(I) salts to give Cu2HgI4.[5]
Nessler's reagent
Named after Julius Nessler, an alkaline solution of K2HgI4 is called Nessler's reagent. This pale solution becomes deeper yellow in the presence of ammonia. At higher concentrations, a brown precipitate may form. The sensitivity as a spot test is about 0.3 μg NH3 in 2 μL.[citation needed]
- NH4+ + 2[HgI4]2− + 4OH− → HgO·Hg(NH2)I ↓(iodide of milans base) + 7I− + 3H2O
The formula for the brown precipitate is given as 3HgO.Hg(NH3)2I2 and as NH2.Hg2I3[6]
Nessler's reagent is generally prepared by combining potassium iodide and mercury(II) chloride.[7] Nessler's reagent may be used with Nessler tubes.
References
- ^ Lide, David R., ed. (2009). CRC Handbook of Chemistry and Physics (90th ed.). Boca Raton, Florida: CRC Press. p. 4-82. ISBN 978-1-4200-9084-0.
- ^ Vogel, Arthur I.; Svehla, G. (1979), Vogel's Textbook of Macro and Semimicro Qualitative Inorganic Analysis (5th ed.), London: Longman, ISBN 0-582-44367-9 – via the Internet Archive
- ^ F. Wagenknecht, R. Juza, "Potassium Triiodomercurate(II)" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1100.
- ^ Mok, K. F.; McKee, V. (1990). "Structure of a dipotassium tetraiodomercurate(II) salt with dibenzo-18-crown-6". Acta Crystallographica C. 46: 2078. doi:10.1107/S0108270190003742.
- ^ F. Wagenknecht, R. Juza, "Copper(I) Tetraiodomercurate(II)" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1100.
- ^ Svehla, G. (1979). Vogel's Textbook of Macro and semimicro qualitative inorganic analysis (5th ed.). London: Longman Group. pp. 293–294. ISBN 0-582-44367-9.
- ^ "Microbiological Investigations". Fisheries and Aquaculture Department, FAO. Retrieved April 25, 2014.