Mercury(I) sulfate, commonly called mercurous sulphate (
UK) or mercurous sulfate (
US) is the
chemical compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
Hg
2SO
4. 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
![Hg2SO4chemdraw](https://upload.wikimedia.org/wikipedia/commons/d/de/Hg2SO4chemdraw.svg)
In the crystal, mercurous sulfate is made up of Hg
22+ center with an Hg-Hg distance of about 2.50 Å. The SO
42− 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
Mercury(I) nitrate is a inorganic compound, a salt of mercury and nitric acid with the formula Hg2(NO3)2. A yellow solid, the compound is used as a precursor to other complexes of Hg22+ complexes.The structure of the hydrate has been determined b ...
with 1 to 6
sulfuric acid
Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...
solution:,
[Google Books result](_blank)
accessed 11 December 2010
:Hg
2(NO
3)
2 + H
2SO
4 → Hg
2SO
4 + 2 HNO
3
It can also be prepared by reacting an excess of
mercury
Mercury commonly refers to:
* Mercury (planet), the nearest planet to the Sun
* Mercury (element), a metallic chemical element with the symbol Hg
* Mercury (mythology), a Roman god
Mercury or The Mercury may also refer to:
Companies
* Merc ...
with concentrated
sulfuric acid
Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...
:
:2 Hg + 2 H
2SO
4 → Hg
2SO
4 + 2 H
2O + SO
2
Use in electrochemical cells
Mercury(I) sulfate is often used in
electrochemical cell
An electrochemical cell is a device capable of either generating electrical energy from chemical reactions or using electrical energy to cause chemical reactions. The electrochemical cells which generate an electric current are called voltaic o ...
s. 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 cell
The Weston standard cell is a wet-chemical cell that produces a highly stable voltage suitable as a laboratory standard for calibration
In measurement technology and metrology, calibration is the comparison of measurement values deliver ...
s 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
In thermochemistry, an endothermic process () is any thermodynamic process with an increase in the enthalpy (or internal energy ) of the system.Oxtoby, D. W; Gillis, H.P., Butler, L. J. (2015).''Principle of Modern Chemistry'', Brooks Cole. p. ...
, 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
{{Sulfates
Sulfates
Mercury(I) compounds