Mercury(I) sulfate

Mercury(I) sulfate
Names
	IUPAC name Mercury(I) sulfate
	Other names Mercurous sulfate
Identifiers
CAS Number	7783-36-0 ;
3D model (JSmol)	Interactive image;
ChemSpider	22951 ;
ECHA InfoCard	100.029.084
EC Number	231-993-0;
PubChem CID	24545;
UNII	PI950N9DYS ;
CompTox Dashboard (EPA)	DTXSID9074565 ;
	InChI InChI=1S/2Hg.H2O4S/c;;1-5(2,3)4/h;;(H2,1,2,3,4)/q2*+1;/p-2 Key: MINVSWONZWKMDC-UHFFFAOYSA-L ;
	SMILES [O-]S(=O)(=O)[O-].[Hg+].[Hg+];
Properties
Chemical formula	Hg2SO4
Molar mass	497.24 g/mol
Appearance	whitish-yellow crystals
Density	7.56 g/cm3
Solubility in water	0.051 g/100 mL (25 °C) ; 0.09 g/100 mL (100 °C)
Solubility	soluble in dilute nitric acid, Insoluble in water, Soluble in hot sulfuric acid.
Magnetic susceptibility (χ)	−123.0·10−6 cm3/mol
Structure
Coordination geometry	monoclinic
Thermochemistry
Heat capacity (C)	132 J·mol−1·K−1[1]
Std molar; entropy (So298)	200.7 J·mol−1·K−1
Std enthalpy of; formation (ΔfH⦵298)	-743.1 kJ·mol−1
Related compounds
Other anions	Mercury(I) fluoride; Mercury(I) chloride; Mercury(I) bromide; Mercury(I) iodide
Other cations	Mercury(II) sulfate; Cadmium sulfate; Thallium(I) sulfate
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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	Infobox references

Mercury(I) sulfate, commonly called mercurous sulphate (UK) or mercurous sulfate (US) is the chemical compound Hg₂SO₄.[2] Mercury(I) sulfate is a metallic compound that is a white, pale yellow or beige powder.[3] 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

The crystal structure of mercurous sulfate is made up of Hg₂²⁺ dumbbells and SO₄²⁻ anions as main building units. Hg₂²⁺ dumbbell is surrounded by four oxygen atoms, with the Hg₋O distance ranging from 2.23 to 2.93 Å, whereas the Hg-Hg distance is about 2.50 Å.[4]

Studies have shown mercury(I) sulfate to have the mercury atoms arranged in doublets with a bond distance of 2.500 Å. The metal atom doublets are oriented parallel to the an axis in a unit cell. Mercury doublets form part of an infinite chain: SO₄ – Hg – Hg – SO₄ – Hg – Hg – … The Hg – Hg – O bond angle is 165°±1°. The chain crosses the unit cell diagonally. The mercury sulfate structure is held together by weak Hg-O interactions. The SO₄ does not act as a single anion, but rather is coordinated to the mercury metal.[5]

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:,[6][7]

Hg₂(NO₃)₂ + H₂SO₄ → Hg₂SO₄ + 2 HNO₃

It can also be prepared by reacting an excess of mercury with concentrated sulfuric acid:[6]

2 Hg + 2 H₂SO₄ → Hg₂SO₄ + 2 H₂O + SO₂

Use in electrochemical cells

Mercury(I) sulfate is often used in electrochemical cells.[8][9][10] It was first introduced in electrochemical cells by Latimer Clark in 1872,[11] It was then alternatively used in Weston cells made by George Augustus Hulett in 1911.[11] It has been found to be a good electrode at high temperatures above 100 °C along with silver sulfate.[12]

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.[13]

References

Lide, David R. (1998), Handbook of Chemistry and Physics (87 ed.), Boca Raton, FL: CRC Press, pp. 5–19, ISBN 0-8493-0594-2
Intermediate Inorganic Chemistry by J. W. Mellor, published by Longmans, Green and Company, London, 1941, page 388
http://www.chemicalbook.com/ChemicalProductProperty_EN_CB0259783.htm
Preparation and Characterization of Dimercury(I)Monofluorophosphate(V), Hg₂PO₃F: Crystal Structure, Thermal Behavior, Vibrational Spectra, and Solid-State ³¹P and ¹⁹F NMR Spectra by Matthias Weil, Michael Puchberger, and Enrique J. Baran, published by Inorg. Chem. 2004, 43. pages 8330–8335
Dorm, E. 1969. Structural studies on mercury(I) compounds. VI. Crystal structure of mercury(I) sulfate and selenate. Acta Chemica Scandinavica (1947–1973) 23:1607–15.
Google Books result, accessed 11 December 2010
Mercurous Sulphate, cadmium sulphate, and the cadmium cell. by Hulett G. A. The physical review.1907. p.19.
"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, Cd_xHg_y | 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
"George Augustus Hulett: from Liquid Crystals to Standard Cell" by John T. Stock. Bull. Hist. Chem. Volume 25, Number 2, 2000, p.91-98
Lietzke, M. H.; Stoughton, R. W. (November 1953). "The Behavior of the Silver—Silver Sulfate and the Mercury—Mercurous Sulfate Electrodes at High Temperatures 1". Journal of the American Chemical Society. 75 (21): 5226–5227. doi:10.1021/ja01117a024.(subscription required)
"Sulphates of Mercury and Standard Cells." by Elliott, R. B. and Hulett, G. A. The Journal of Physical Chemistry 36.7 (1932): 2083–2086.

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[hand2-1] Lide, David R. (1998), Handbook of Chemistry and Physics (87 ed.), Boca Raton, FL: CRC Press, pp. 5–19, ISBN 0-8493-0594-2

[2] Intermediate Inorganic Chemistry by J. W. Mellor, published by Longmans, Green and Company, London, 1941, page 388

[3] ttp://www.chemicalbook.com/ChemicalProductProperty_EN_CB0259783.htm

[4] Preparation and Characterization of Dimercury(I)Monofluorophosphate(V), Hg₂PO₃F: Crystal Structure, Thermal Behavior, Vibrational Spectra, and Solid-State ³¹P and ¹⁹F NMR Spectra by Matthias Weil, Michael Puchberger, and Enrique J. Baran, published by Inorg. Chem. 2004, 43. pages 8330–8335

[5] Dorm, E. 1969. Structural studies on mercury(I) compounds. VI. Crystal structure of mercury(I) sulfate and selenate. Acta Chemica Scandinavica (1947–1973) 23:1607–15.

[google-6] Google Books result, accessed 11 December 2010

[7] Mercurous Sulphate, cadmium sulphate, and the cadmium cell. by Hulett G. A. The physical review.1907. p.19.

[8] "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

[9] "Electromotive Force Studies of Cell, Cd_xHg_y | 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

[10] "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

[GEORGE_AUGUSTUS_HULETT_2000,_p.91-98-11] "George Augustus Hulett: from Liquid Crystals to Standard Cell" by John T. Stock. Bull. Hist. Chem. Volume 25, Number 2, 2000, p.91-98

[12] Lietzke, M. H.; Stoughton, R. W. (November 1953). "The Behavior of the Silver—Silver Sulfate and the Mercury—Mercurous Sulfate Electrodes at High Temperatures 1". Journal of the American Chemical Society. 75 (21): 5226–5227. doi:10.1021/ja01117a024.(subscription required)

[13] "Sulphates of Mercury and Standard Cells." by Elliott, R. B. and Hulett, G. A. The Journal of Physical Chemistry 36.7 (1932): 2083–2086.