Sulfate
Author: Hans-Jürgen Schwarz
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Overview[edit]
In this overview the most frequently occurring salts with sulphate as the anion are listed. The various salt phases are discussed in detail on separate pages, their occurrence and their damage potential is explained and the damage symptoms are illustrated in a documentation.
| Salt | Formula | Solubility at 20°C | Deliquescence RH | Light refraction | Birefringence | Notes |
|---|---|---|---|---|---|---|
| Bassanite | CaSO4•0.5H2O | 3.0 g/l | no = 1.558 ne = 1.586 |
Δ = 0.028 | hardly soluble in water | |
| Boussingaultite | (NH4)2Mg(SO4)2•6H2O | 159 g/l (0°C), 1300 g/l (100°C) | nx = 1.472 ny = 1.473 nz = 1.479 |
Δ = 0.007 | ||
| Epsomite | MgSO4•7H2O | 2.893 mol/kg | nx = 1.432 ny = 1.453 nz = 1.4609 |
Δ = 0.0284 | can be produced from an aqueous solution under 50°C | |
| Ettringite | Ca6Al2(SO4)3(OH)12•26H2O | no = 1.491 ne = 1.470 |
Δ = 0.021 | insoluble in water | ||
| Gypsum | CaSO4•2H2O | 2.14 g/l | α = 1.5207 β = 1.5230 γ = 1.5299 |
Δ = 0.0092 | ||
| Mirabilite | Na2SO4•10H2O | 1.353 mol/kg | nx = 1.394 ny = 1.396 nz = 1.398 |
Δ = 0.004 | soluble in water and glycerin, insoluble in pure alcohol easily loses some water, converts to thenardite at 32°C abnormal blue or brown interference colors | |
| Pentahydrite | MgSO4•5H2O | nx = 1.482 ny = 1.492 nz = 1.493 |
Δ = 0.011 | unstable in air | ||
| Schönite | K2Mg(SO4)2•6H2O | 250 g/l | nx = 1.4607 ny = 1.4629 nz = 1.4755 |
Δ = 0.0148 | ||
| Thaumasite | Ca3Si(OH)6(CO3)(SO4)• 12H2O |
no = 1.491 ne = 1.470 |
Δ = 0.039 | insoluble in water | ||
| Thenardite | Na2SO4 | 162 g/l | nx = 1.468 ny = 1.473 nz = 1.483 |
Δ = 0.015 | soluble in water and glycerin, insoluble in pure alcohol | |
| Hexahydrite | MgSO4•6H2O | 3.611 mol/kg | α = 1.426 β = 1.453 γ = 1.456 |
Δ = 0.030 | can be produced from an aqueous solution between 48-69 °C | |
| Arcanite | K2SO4 | 111.5 g/l | nx = 1.494 ny = 1.495 nz = 1.497 |
Δ = 0.003 | ||
| Aphthitalite | K3Na(SO4)2 Na2SO4•3K2SO4 |
no = 1.491 ne = 1.499 |
Δ = 0.008 | |||
| Astrakanite | Na2Mg(SO4)2•4H2O | nx = 1.483 ny = 1.486 nz = 1.487 |
Δ = 0.004 | |||
| Darapskite | Na3(SO4)(NO3)•H2O NaNO3•Na2SO4•H2O |
nx = 1.391 ny = 1.481 nz = 1.486 |
Δ = 0.095 | can be produced from an aqueous solution of Na2SO4 and NaNO3 at 14-50°C | ||
| Glauberite | Na2Ca(SO4)2 | nx=1.515 ny=1.535 nz=1.536 |
Δ=0.021 | |||
| Gorgeyite | K2Ca5(SO4)6•H2O | nx= 1.560 ny = 1.569 nz = 1.584 |
Δ = 0.024 | |||
| Leonite | K2Mg(SO4)2•4H2O | nx=1.479 ny=1.483 nz=1.487 |
Δ=0.008 | |||
| Syngenite | K2Ca(SO4)2•H2O | 2.5 g/l | nx = 1.501 ny = 1.516 nz = 1.517 |
Δ = 0.016 | ||
| Anhydrite | CaSO4 | nx=1.5698 ny=1.5754 nz=1.6136 |
Δ=0.0438 | |||
| Starkeyite | MgSO4•4H2O | nx = 1.49 ny = 1.491 nz = 1.497 |
Δ = 0.007 | unstable in air | ||
| Sodium sulfate heptahydrate | Na2SO4•7H2O | 3.143 mol/kg | ||||
| Kieserite | MgSO4•H2O | 5.600 mol/kg | nx = 1.520 ny = 1.533 nz = 1.584 |
Δ = 0.064 | can be produced from an aqueous solution over 67°C | |
| Magnesium sulfate | ||||||
| Meridianiite | MgSO4•4H2O | |||||
| Sodium sulfate | ||||||
| Sodium sulfate phase III | Na2SO4 | 4.428 mol/kg |