Chloroosmic acid (also known as hexachloroosmic acid, and dihydrogen hexachloroosmate) is an inorganic chemical compound with the chemical formula . It exists as a dark deliquescent solid. It forms a hexahydrate.
Synthesis Hexachloroosmic acid can be prepared by reducing osmium tetroxide in hydrochloric acid with alcohol and heating. Ferrous chloride is sometimes used in place of alcohol. + 4 + 10HCl → + 4 + 4
Another way of preparing it is by dissolving osmium dioxide in hydrochloric acid. + 6HCl → + 2
Solid crystals of the acid can be isolated upon cooling after boiling its solutions down to a syrup.
Reactions When strong alkali is added to hexachloroosmic acid, it decomposes and precipitates osmium dioxide.
It also reacts with alkali chlorides to yield hexachloroosmate salts, such as ammonium hexachloroosmate(IV).
The coordination complex can be made by reacting chloroosmic acid in ethanol with dimethyl sulfoxide.
Salts Hexachloroosmates vary in color both in and out of solution depending on the cation. While solutions of the acid possess an amber-orange color, solutions of hexachloroosmate salts are yellow, sodium being the exception which forms deep red solutions. When isolated the sodium, potassium, rubidium, and ammonium salts are all red, while the cesium, silver, and thallium salts are orange, green-brown, and orange-green respectively. It also forms salts with many complex organic cations, yielding yellow, orange, red, and brown crystals.
References