Potassium tetraiodomercurate(II)

Potassium tetraiodomercurate(II)
Potassium tetraiodomercurate(II)
Identifiers
CAS number 7783-33-7
UN number 3287
Properties
Molecular formula HgI4K2
Molar mass 786.4 g mol−1
Density 1.16 g/cm3
Hazards
MSDS External MSDS for Nessler's reagent
Related compounds
Other anions Mercury(II) iodide
 YesY tetraiodomercurate(II) (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references
The tetraiodomercurate(II) anion

Potassium tetraiodomercurate(II) is an inorganic compound containing potassium cations and the tetraiodomercurate(II) complex 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.


Contents

Nessler's reagent

Named after Julius Neßler, when this solution gives a yellow coloration, it indicates 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 + 7I + 3H2O

Nessler's reagent is generally prepared from potassium iodide and mercury(II) chloride. A hot concentrated solution of mercury(II) chloride is added to concentrated solution of potassium iodide, until the precipitate of mercury(II) iodide stops dissolving. The liquid is filtered, and potassium hydroxide and a further bit of mercury(II) chloride solution are added. The resulting solution is then cooled and diluted to required concentration.[1] Nessler's reagent may be used with Nessler tubes.

References

  1. ^ http://www.fao.org/docrep/field/003/Q6501E/Q6501E05.htm
  • 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 

Further reading

  • 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. 

External links


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