potassium mercuric iodide,
Nessler's reagent (principal component)
3D model (JSmol)
|Solubility||soluble in alcohol, ether, acetone|
|Safety data sheet||External MSDS for Nessler's reagent|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
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.
Crystallizing from a concentrated aqueous solution of mercuric iodide with potassium iodide is the monohydrate KHgI3.H2O, which is pale orange. In aqueous solution this triodido complex adds iodide to give the tetrahedral tetraiodo dianion.
Solutions of K2HgI4 react with Cu(I) salts to give Cu2HgI4.
Named after Julius Nessler, an alkalic 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 ?g NH3 in 2 ?L.