Mercury(II) potassium iodide is used as a pharmaceutical intermediate. It is also used as reagents, chemical research and organic intermediates.
Nessler's reagent (K2[HgI4]) is used to detect the presence of ammonia, particularly in very small amounts.
It is prepared by mixing 2g potassium iodide in 5ml water. To this solution, 3g of mercury (II) iodide is added, and the resulting solution is made to 20ml. Finally, 40g potassium hydroxide (30 %) is added to provide the alkaline base.
Nessler's Reagent is a periodometallate salt that is solution of mercuric iodide in potassium iodide. It contains a tetraiodomercurate(2-).
Mercuric potassium iodide, [solid] appears as odorless yellow crystals. Crystallizes with either one, two or three molecules of water. Soluble in water and denser than water. Commercially available in the anhydrous form. Highly toxic by ingestion, inhalation, and skin absorption.
Deliquescent. Very water soluble.
MERCURIC POTASSIUM IODIDE is incompatible with acetylene, ammonia, chlorine dioxide, azides, calcium (amalgam formation), sodium carbide, lithium, rubidium, copper . NESSLER'S REAGENT behave in aqueous solution as a weak acid.
Highly toxic by ingestion, inhalation, and
skin absorption.
Highly toxic, may be fatal if inhaled, swallowed or absorbed through skin. Avoid any skin contact. Effects of contact or inhalation may be delayed. Fire may produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause pollution.
Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. Containers may explode when heated. Runoff may pollute waterways.
A poison. Moderately
toxic by skin contact and intraperitoneal
routes. When heated to decomposition it
emits very toxic fumes of Hg, K2O, and I-.
See also MERCURY.
