Silver sulfate

Silver sulfate

Silver(I) sulfate sample and original bottle.
Names
IUPAC name Silver sulfate
Other names Disilver(1+) sulfate Silver(I) sulfate
Identifiers
Jmol-3D images	Image
SMILES [Ag+].[Ag+].[O-]S([O-])(=O)=O
Properties
Chemical formula	Ag2SO4
Molar mass	311.799 g/mol
Appearance	White solid
Odor	Odorless
Density	5.45 g/cm3 (at 20 °C)
Melting point	652.2–660.0 °C (1,206.0–1,220.0 °F; 925.4–933.1 K)
Boiling point	1,085 °C (1,985 °F; 1,358 K)
Solubility in water	0.57 g/100 mL (0 °C) 0.69 g/100 mL (10 °C) 0.83 g/100 mL (25 °C) 0.96 g/100 mL (40 °C) 1.33 g/100 mL (100 °C)
Solubility	Soluble in conc. sulfuric acid Slightly soluble in acetates, acetone, alcohols, amides, aq. acids, diethyl ether Insoluble in ethanol
Vapor pressure	~0 mmHg
Thermochemistry
Std molar entropy (So298)	200.4 kJ/mol
Std enthalpy of formation (ΔfHo298)	−715.9 kJ/mol
Hazards
Safety data sheet	ScienceLab
Flash point	Non-flammable
Related compounds
Related compounds	Silver nitrate Silver perchlorate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Silver sulfate is an ionic compound of silver with the formula Ag₂SO₄, mainly used in silver plating and as a non-staining substitute to silver nitrate. It is also used in analytical chemistry.

Properties

Chemical

Silver sulfate darkens upon exposure to strong light, though this process requires many hours.

Silver sulfate will react with an aq. solution of NaOH to yield silver oxide, under strong stirring, which can work even if the silver sulfate is not fully dissolved in water, as all the dissolved silver from the solution that precipitates is immediately replaced by more silver that further dissolves in the solution. However, for the reaction to be complete, the silver sulfate particles must be very fine, as any large pieces of silver sulfate will get coated by silver oxide, which blocks the displacement reaction.

Ag₂SO₄ + 2 NaOH → Ag₂O + Na₂SO₄ + H₂O

Physical

Silver sulfate is a white solid, extremely poorly soluble in water (0.83 g/100 ml at 25 °C), but soluble in concentrated sulfuric acid. It is quite stable under ordinary conditions of use and storage, though it darkens upon exposure to air or light.

Availability

Silver sulfate is sold by various chemical suppliers, though it's not cheap.

Preparation

Silver sulfate can be prepared by reacting concentrated sulfuric acid with silver nitrate:

2 AgNO₃ + H₂SO₄ → Ag₂SO₄ + 2 HNO₃

Alternatively, a sulfate salt, like sodium sulfate can be used instead of sulfuric acid.

2 AgNO₃ + Na₂SO₄ → Ag₂SO₄ + 2 NaNO₃

Hot sulfuric acid will dissolve silver metal, forming silver sulfate:

2 Ag + 2 H₂SO₄ → Ag₂SO₄ + SO₂ + 2 H₂O

Projects

• Silver plating
• Compound collecting

Handling

Safety

Silver sulfate should not be handled without protection, as it will darken when exposed to light, thus staining the skin.

Storage

Silver sulfate should be kept in closed bottles, away from light and air.

Disposal

Best to recycle it.

References

Relevant Sciencemadness threads

• Silver sulfate
• Sulphur trioxide from silver sulphate
• Silver sulfate