Iron(II) sulfate

Athanor · official

FeO₄S · 151.91 g/mol

IUPAC name: iron(2+) sulfate

Also called ferrous sulfate, green vitriol

Inorganic

Open in Athanor

Drawn from its SMILES with RDKit

WarningHarmful if swallowed · Causes skin irritation · Causes serious eye irritation

Names and identifiers

IUPAC name: iron(2+) sulfate
Synonyms: ferrous sulfate, green vitriol, FERROUS SULFATE
+ 37 more
Ferrous sulphate, Iron(2+) sulfate, Ferrous sulfate anhydrous, Iron sulphate, Ferrosulfate, Iron sulfate (1:1), Combiron, Duretter, Duroferon, Ferobuff, Ferralyn, Fersolate, Ferolix, Ferulen, Ferusal, Irospan, Kesuka, Odophos, Sal chalybis, Ferro-Theron, Iron monosulfate, Sorbifer durules, FeSO4, Slow Fe, Quickfloc (salt), Iron(II) sulfate (1:1), Iron sulfate (FeSO4), Ferrous sulfate (1:1), Ferrosulfat, Sulfuric acid, iron(2+) salt (1:1), Exsiccated ferrous sulphate, Iron(2+) sulfate (1:1), DTXSID0029688, SFE 171, 2IDP3X9OUD, Iron (as sulphate), Ferrous sulfate,dried
Molecular formula: FeO₄S
Empirical formula: FeO₄S
Molecular weight: 151.91 g/mol
Exact mass: 151.88666
CAS number: 7720-78-7
PubChem CID: 24393
Canonical SMILES: [O-]S(=O)(=O)[O-].[Fe+2]
Isomeric SMILES: [O-]S(=O)(=O)[O-].[Fe+2]
InChI: InChI=1S/Fe.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2
InChIKey: BAUYGSIQEAFULO-UHFFFAOYSA-L
Molfile

Names, InChI and the identifiers from PubChem, retrieved 2026-10-14.

Physical properties

TemperaturePressureDensity

Appearance: Ferrous sulfate appears as a greenish or yellow-brown crystalline solid. Density 15.0 lb /gal. Melts at 64 °C and loses the seven waters of hydration at 90 °C. The primary hazard is the threat to the environment. Immediate steps should be taken to limit its spread to the environment. Used for water or sewage treatment, as a fertilizer ingredient.[1]
2 values
From CAMEO Chemicals, the most authoritative source here.
Value As written Source
–shown Ferrous sulfate appears as a greenish or yellow-brown crystalline solid. Density 15.0 lb /gal. Melts at 64 °C and loses the seven waters of hydration at 90 °C. The primary hazard is the threat to the environment. Immediate steps should be taken to limit its spread to the environment. Used for water or sewage treatment, as a fertilizer ingredient. [1] CAMEO Chemicals
– Large Crystals; CBI; Dry Powder; Other Solid; Liquid; Dry Powder; Large Crystals [2] EPA Chemical Data Reporting (CDR)
Density: 3.65 @25 °C[4]
2 values
Sources disagree; from PAC Chemical Database, U.S. Department of Energy, the most authoritative.
Value As written Source
– 1.9 at 59 °F (USCG, 1999) - Denser than water [1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
–shown 3.65 @25 °C [4] PAC Chemical Database, U.S. Department of Energy
Autoignition temperature: Reported, but no value passed the checks.
The value and why
Not flammable (USCG, 1999) (could not be read; source [1])

Value	As written	Source
–shown	Ferrous sulfate appears as a greenish or yellow-brown crystalline solid. Density 15.0 lb /gal. Melts at 64 °C and loses the seven waters of hydration at 90 °C. The primary hazard is the threat to the environment. Immediate steps should be taken to limit its spread to the environment. Used for water or sewage treatment, as a fertilizer ingredient.	[1] CAMEO Chemicals
–	Large Crystals; CBI; Dry Powder; Other Solid; Liquid; Dry Powder; Large Crystals	[2] EPA Chemical Data Reporting (CDR)

Value	As written	Source
–	1.9 at 59 °F (USCG, 1999) - Denser than water	[1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
–shown	3.65 @25 °C	[4] PAC Chemical Database, U.S. Department of Energy

Each value as its source reports it, with the source's number after it (listed under References). Where several sources report a property, the row shows the value most of them agree on, the rule the app uses; open the values to see every one.

Calculated

Heavy atoms: 6
Rings: 0
Aromatic rings: 0
Fraction sp³ carbons (Fsp3): 0
H-bond donors: 0
H-bond acceptors: 4
Rotatable bonds: 0
TPSA (Å²): 80.3 computed here · PubChem 88.6
Formal charge: 0
Complexity: 62 PubChem
Stereocenters: None
Double-bond geometry: None specified
Point group: Td of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

Fe36.76%
O42.13%
S21.11%

Isotope pattern

Each peak is a nominal mass with its abundance-weighted exact mass, as a percentage of the tallest, from IUPAC natural isotope abundances.

Computed from the structure with RDKit 2026.09 when this page was built, beside PubChem's own computed values from its record; where the two differ, both are shown.

Predicted

log P: -1.34 Crippen (Wildman and Crippen 1999)
log S (water solubility): 0.06 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 4.2 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 151.91
log P ≤ 5 (Crippen): -1.34
H-bond donors ≤ 5: 0
H-bond acceptors ≤ 10: 4

Passes all four rules.

Predictions, not measurements; each names its method. A measured log P, where a source reports one, is under Physical properties.

Safety

Warning

Harmonized EU classification (CLP Annex VI). Source [5].

Harmful or irritant

H302Harmful if swallowed
H315Causes skin irritation
H319Causes serious eye irritation

Precautionary statements: P264, P264+P265, P270, P280, P301+P317, P302+P352, P305+P351+P338, P321, P330, P332+P317, P337+P317, P362+P364, P501

View all classifications (4)

[5] Regulation (EC) No 1272/2008 of the European Parliament and of the Council · WarningH302, H315, H319
[6] European Chemicals Agency (ECHA)This chemical does not meet GHS hazard criteria for 0.2% (4 of 2130) of reports.
[6] European Chemicals Agency (ECHA) · 2,130 reports · WarningH302, H315, H319
[6] European Chemicals Agency (ECHA) · 3 reportsThis chemical does not meet GHS hazard criteria for 100% (3 of 3) of all reports.

First aid

Ingestion: Give milk immediately and then induce vomiting by stroking the pharynx with a blunt object such as a spoon handle. Gastric lavage with 1 pint of 5% aqueous solution of mono- or disodium phosphate if promptly available; otherwise use water. Get medical attention. (USCG, 1999)[1]

Storage

Store in tight containers.[3]

Incompatibilities

May ignite on contact with arsenic trioxide and sodium nitrate.[3]
Potentially explosive reacition with methyl isocyanoacetate at 25 °C[3]

Safety data sheets on the supplier’s page: A2B Chem, Alfa Chemistry, LGC Standards.

Always read the supplier’s safety data sheet before working with it.

Spectra

FTIRSpectraBase (KBr WAFER)

Experimental spectra held by these sources; each link opens the source's own record.

Literature

Reading PubChem, OpenAlex and GSRS…

Bioactivity

Reading ChEMBL…

References

[1]CAMEO Chemicals · Public domain (NOAA) · via PubChem · retrieved 2026-10-14
[2]EPA Chemical Data Reporting (CDR) · Public domain (US EPA) · via PubChem · retrieved 2026-10-14
[3]Hazardous Substances Data Bank (HSDB) · Public domain (US NLM) · via PubChem · retrieved 2026-10-14
[4]PAC Chemical Database, U.S. Department of Energy · Public domain (US DOE) · via PubChem · retrieved 2026-10-14
[5]Regulation (EC) No 1272/2008 of the European Parliament and of the Council · EU reuse policy, CC BY 4.0 · via PubChem · retrieved 2026-10-14
[6]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
[7]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
·Calculated values: computed by Athanor with RDKit 2026.09 from the structure.
·Literature on PubChem

Data last updated 2026-10-14.