Ferric oxalate
CAS 2944-66-3 · EC 220-951-7
Also known as iron(III) oxalate, diiron trioxalate
Only one notification in the C&L Inventory; very low evidence base. Hexahydrate 166897-40-1 not queried.
Handle chemistry safely
Wear gloves and eye protection, work with good ventilation, and read the supplier’s safety data sheet before use. Hazard information here is a summary, not a replacement for it. Dispose of all photographic chemistry correctly, in line with local laws and your local authority’s guidance. Never mix waste solutions, and check the supplier’s safety data sheet before disposing of anything.
Hazards
There is no official EU classification. Shown is the classification most companies have notified to ECHA: 100.0% of notifications, 1 distinct classifications notified.
Signal word: Warning
Harmful or irritant
- H312 Harmful in contact with skin.
- H302 Harmful if swallowed.
UK and EU rules
- UK Poisons Act 1972: reportable poison – "metallic oxalates" entry (GOV.UK list of chemicals)
Photographic uses
- kallitype sensitiser
- platinum/palladium sensitiser
Sources
- ECHA CHEM substance record: Diiron trioxalate (100.019.047)
- ECHA CHEM – C&L Inventory (harmonised CLP Annex VI and notified classifications) and legal obligations (chem.echa.europa.eu APIs: /api-cnl-inventory/harmonized|industry, /api-obligation-substance/v1)
- Supplying explosives precursors and poison substances: list of chemicals (supplying-explosives-precursors/list-of-chemicals (updated 3 July 2026))
Checked October 2026.