Chromium compounds

Chromium compounds are chemical compounds containing chromium ions. Chromium occurs in several oxidation states; +2, +3, and +6 are most common.

Chromium oxides

• Chromium(II) oxide, black, rare, reducing agent
• Chromium(III) oxide, dark green
• Chromium(IV) oxide, black, used in cassettes
• Chromium(VI) oxide, chromium trioxide, red, oxidizing agent, toxic

Chromium acids

• Chromic acid, dissolving of chromium(VI) oxide in water

Other chromium(II) compounds

• Chromium(II) chloride, blue when dissolved in water, unstable

Other chromium(III) compounds

• Chromium(III) chloride, green when containing water (hydrated), purple when not containing water (anhydrous)
• Chromium(III) sulfate
• Chrome alum

Other chromium(VI) compounds

• Chromyl chloride, red liquid

Chromates and dichromates

Chromates are generally yellow, while dichromates are red or orange. Both are toxic and oxidizing agents.

Chromates

The chromate ion is CrO₄^2-.

• Potassium chromate
• Sodium chromate

Dichromates

The dichromate ion is Cr₂O₇^2-.

• Ammonium dichromate
• Potassium dichromate
• Sodium dichromate, used in chromium processing