Acid |
Formula |
Formal oxidation number |
Structure |
Related anions |
Notes |
Sulfuric acid |
H2SO4 |
+6 |
|
Sulfate, SO2− 4 and hydrogen sulfate commonly known as bisulfate, HSO− 4 |
Best known and industrially significant. |
Polysulfuric acids including disulfuric acid (pyrosulfuric acid) |
H2SO4·nSO3 |
+6 |
|
Disulfate (commonly known as pyrosulfate), S 2O2− 7 and trisulfate, S 3O2− 10 |
Pure disulfuric acid melts at 36 °C. Present in fuming sulfuric acid, oleum. Examples known for n = 1 and n = 2. |
Peroxymonosulfuric acid |
H2SO5 |
+6 |
|
Peroxomonosulfate, OOSO2− 3 |
"Caro's acid", a solid melting at 45 °C |
Peroxydisulfuric acid |
H2S2O8 |
+6 |
|
Peroxydisulfate, O 3SOOSO2− 3 |
"Marshall's acid", a solid melting at 65 °C. |
Dithionic acid |
H2S2O6 |
+5 |
|
Dithionate, O 3SSO2− 3 |
Not isolated in pure form, only concentrated solutions have been prepared |
Thiosulfuric acid |
H2S2O3 |
0 (for the terminal sulfur), +4 (for the central atom) |
|
Thiosulfate, S 2O2− 3 Hydrogenthiosulfate HS 2O− 3 (ammonium salt prepared in anhydrous methanol at −80 °C[1]) |
Aqueous solutions decompose. |
Disulfurous acid or pyrosulfurous acid |
H2S2O5 |
+5 (of the sulfur atom bonded to 3 oxygen atoms), +3 (of other sulfur atom) |
|
Disulfite commonly known as metabisulfite, S 2O2− 5 |
Not known. |
Sulfurous acid |
H2SO3 |
+4 |
|
Bisulfite, HSO− 3 and sulfite, SO2− 3 |
Not known. |
Dithionous acid |
H2S2O4 |
+3 |
|
Dithionite, O 2SSO2− 2 |
Not known. |
Sulfoxylic acid |
H2SO2 |
+2 |
|
Sulfoxylate, SO2− 2 |
Free acid not known |
Polythionic acid |
H2SxO6 |
0 (for the bridging S atoms), +5 (for the terminal central S atoms) |
|
Polythionates, O 3S(S x−2)SO2− 3. Example trithionate, tetrathionate, pentathionate, hexathionate, heptathionate, octathionate, nonathionate, decathionate, undecathionate, dodecathionate, tridecathionate, and tetradecathionate. |
Examples known with x = 3, 4, 5, 6, 7, 8, 10, 12, 14. |
Thiosulfurous acid |
H2S2O2 |
−1 (for the exterior sulfur atom ), +3 (for the central atom) |
|
Thiosulfites |
Not known |
Dihydroxydisulfane |
H2S2O2 |
+1 |
|
|
Acid known |