Mercury(I) sulfate, commonly called mercurous sulphate (UK) or mercurous sulfate (US) is the chemical compound Hg2SO4.Intermediate Inorganic Chemistry by J. W. Mellor, published by Longmans, Green and Company, London, 1941, page 388 Mercury(I) sulfate is a metallic compound that is a white, pale yellow or beige powder. It is a metallic salt of sulfuric acid formed by replacing both hydrogen atoms with mercury(I). It is highly toxic; it could be fatal if inhaled, ingested, or absorbed by skin.
Structure
In the crystal, mercurous sulfate is made up of Hg22+ center with an Hg-Hg distance of about 2.50 Å. The SO42− anions form both long and short Hg-O bonds ranging from 2.23 to 2.93 Å.
Focusing on the shorter Hg-O bonds, the Hg – Hg – O bond angle is 165°±1°.
Preparation One way to prepare mercury(I) sulfate is to mix the acidic solution of mercury(I) nitrate with 1 to 6 sulfuric acid solution:,Google Books result, accessed 11 December 2010Mercurous Sulphate, cadmium sulphate, and the cadmium cell. by Hulett G. A. The physical review.1907. p.19.
It can also be prepared by reacting an excess of mercury with concentrated sulfuric acid:
Use in electrochemical cells Mercury(I) sulfate is often used in electrochemical cells."Influence of Microstucture on the Charge Storage Properties of Chemically Synthesized Manganese Dioxide" by Mathieu Toupin, Thiery Brousse, and Daniel Belanger. Chem. Mater. 2002, 14, 3945–3952"Electromotive Force Studies of Cell, CdxHgy | CdSO4,(m) I Hg2SO4, Hg, in Dioxane-Water Media" by Somesh Chakrabarti and Sukumar Aditya. Journal of Chemical and Engineering Data, Vol.17, No. 1, 1972"Characterization of Lithium Sulfate as an Unsymmetrical-Valence Salt Bridge for the Minimization of Liquid Junction Potentials in Aqueous – Organic Solvent Mixtures" by Cristiana L. Faverio, Patrizia R. Mussini, and Torquato Mussini. Anal. Chem. 1998, 70, 2589–2595 It was first introduced in electrochemical cells by Latimer Clark in 1872,"George Augustus Hulett: from Liquid Crystals to Standard Cell" by John T. Stock. Bull. Hist. Chem. Volume 25, Number 2, 2000, p.91-98 It was then alternatively used in Weston cells made by George Augustus Hulett in 1911. It has been found to be a good electrode at high temperatures above 100 °C along with silver sulfate.
Mercury(I) sulfate has been found to decompose at high temperatures. The decomposition process is endothermic, and it occurs between 335 °C and 500 °C.
Mercury(I) sulfate has unique properties that make the standard cells possible. It has a rather low solubility (about one gram per liter); diffusion from the cathode system is not excessive; and it is sufficient to give a large potential at a mercury electrode."Sulphates of Mercury and Standard Cells." by Elliott, R. B. and Hulett, G. A. The Journal of Physical Chemistry 36.7 (1932): 2083–2086.
References