Sodium hydroxide

CAS 1310-73-2 · EC 215-185-5 · HNaO

Also known as caustic soda, lye

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

Official EU classification (harmonised under CLP Annex VI).

Signal word: Danger

Corrosive

H314 Causes severe skin burns and eye damage.

UK and EU rules

UK Poisons Act 1972: reportable poison – sodium hydroxide at 12% w/w caustic alkalinity (GOV.UK list of chemicals, 3 July 2026)

Photographic uses

strong alkali (Parodinal, D-8)

Sources

ECHA CHEM substance record: Sodium hydroxide (100.013.805)
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.