Mercury(I) sulfate

Mercury(I) sulfate

Names
IUPAC name Mercury(I) sulfate
Other names Mercurous sulfate
Identifiers
CAS Number	7783-36-0 Y
3D model (JSmol)	Interactive image
ChemSpider	22951 N
ECHA InfoCard	100.029.084
EC Number	231-993-0
PubChem CID	24545
InChI InChI=1S/2Hg.H2O4S/c;;1-5(2,3)4/h;;(H2,1,2,3,4)/q2*+1;/p-2 N Key: MINVSWONZWKMDC-UHFFFAOYSA-L N
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
Specific 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 (ΔfHo298)	-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).
N verify (what is YN ?)
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 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 Hg₋O distance ranging from 2.23 to 2.93 Å, whereas Hg-Hg distance is approximately 2.500Å.^[4] Studies have shown mercury(I) sulfate to have the mercury atoms arranged in doublets with a bond distance of 2.500Å. The metal atom doublets are oriented parallel to the an axis in a unit cell. Mercury doublets form part of 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 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 mady 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 was found to decompose at high temperatures. The decomposition process is endothermic and occurs between 335 and 500. Mercury(I) sulfate has unique properties that make the standard cells possible. It has a rather small solubility (about a gram per liter) that diffusion from the cathode system is not excessive, and it is sufficient to give a large potential at a mercury electrode.^[13]

References