Ammonium dichromate

CAS 7789-09-5 · EC 232-143-1 · Cr2H8N2O7

Also known as ammonium bichromate

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

Oxidising · Serious health hazard · Acute toxicity · Corrosive · Hazardous to the environment

H272 May intensify fire; oxidiser.
H350 May cause cancer.
H340 May cause genetic defects.
H360FD May damage fertility. May damage the unborn child.
H330 Fatal if inhaled.
H312 Harmful in contact with skin.
H301 Toxic if swallowed.
H372 Causes damage to organs through prolonged or repeated exposure.
H314 Causes severe skin burns and eye damage.
H334 May cause allergy or asthma symptoms or breathing difficulties if inhaled.
H317 May cause an allergic skin reaction.
H410 Very toxic to aquatic life with long lasting effects.

UK and EU rules

REACH Annex XIV entry 20
REACH Annex XIV (Authorisation List) – sunset date 21-Sep-2017, latest application date 21-Mar-2016 – use in the EU requires an authorisation
UK REACH Annex 14: retained (all EU Annex XIV entries at 31 Dec 2020 were carried over – HSE)
REACH Candidate List (SVHC)
ECHA CHEM also links an indirect entry on the REACH Annex XVII Restriction List (specific entry not resolved)

Photographic uses

gum bichromate sensitiser
carbon transfer sensitiser
contrast agent in new cyanotype (0.1 g per 100 ml)

Used in: New cyanotype (Mike Ware)

Sources

Checked October 2026.