Mercury(II) sulfate, commonly called mercuric sulfate, is the chemical compound HgSO<sub>4</sub>. It is an odorless salt that forms white granules or crystalline powder. In water, it separates into an insoluble basic sulfate with a yellow color and sulfuric acid.
The anhydrous compound features Hg<sup>2+</sup> in a highly distorted tetrahedral HgO<sub>4</sub> environment. Two HgâÂÂO distances are 2.22 àand the others are 2.28 and 2.42 à. In the monohydrate, Hg<sup>2+</sup> adopts a linear coordination geometry with HgâÂÂO (sulfate) and HgâÂÂO (water) bond lengths of 2.179 and 2.228 àrespectively. Four weaker bonds are also observed with HgâÂÂO distances >2.5 à.
In 1932, the Japanese chemical company Chisso Corporation began using mercury sulfate as the catalyst for the production of acetaldehyde from acetylene and water. Though it was unknown at the time, methylmercury is formed as a side product of this reaction. Exposure and consumption of the mercury waste products, including methylmercury, that were dumped into Minamata Bay by Chisso are believed to be the cause of Minamata disease in Minamata, Japan.
Mercury sulfate can be produced by treating mercury with hot concentrated sulfuric acid:
Alternatively yellow mercuric oxide reacts also with concentrated sulfuric acid.
An acidic solution of mercury sulfate is known as Denigés' reagent. It was commonly used throughout the 20th century as a qualitative analysis reagent. If Denigés' reagent is added to a solution containing compounds that have tertiary alcohols, a yellow or red precipitate will form.
Mercury sulfate, as well as other mercury(II) compounds, are commonly used as catalysts in oxymercuration-demercuration, a type of electrophilic addition reaction that results in hydration of an unsaturated compound. The hydration of an alkene gives an alcohol. The regioselectivity is that predicted by Markovnikov's rule. For an alkyne, the result is an enol, which tautomerizes to give the carbonyl. At one time, this chemistry was employed commercially for the preparation of acetaldehyde from acetylene:
A related and specialized example is the conversion of 2,5-dimethylhexyne-2,5-diol to 2,2,5,5-tetramethyltetrahydrofuran using aqueous mercury sulfate without the addition of acid.
Inhalation of HgSO<sub>4</sub> can result in acute poisoning: causing tightness in the chest, difficulties breathing, coughing and pain. Exposure of HgSO<sub>4</sub> to the eyes can cause ulceration of conjunctiva and cornea. If mercury sulfate is exposed to the skin it may cause sensitization dermatitis. Lastly, ingestion of mercury sulfate will cause necrosis, pain, vomiting, and severe purging. Ingestion can result in death within a few hours due to peripheral vascular collapse.
It was used in the late 19th century to induce vomiting for medical reasons.