Iron II vs. Iron III Chloride: Key Differences & Uses
Iron II chloride (FeCl₂) and Iron III chloride (FeCl₃) are two salts of iron that differ by one electron: Fe²⁺ versus Fe³⁺, turning pale green crystals into brown-black flakes.
DIY etchers often grab the wrong bottle and wonder why their copper PCB turns blotchy; photographers swapping solutions mix them and ruin negatives because both dissolve in water yet react differently with metals.
Key Differences
FeCl₂ carries a +2 charge, forms pale green hydrates, and works as a gentle reducing agent. FeCl₃ holds +3, appears dark brown, acts as an oxidizer, and stains skin bright orange.
Which One Should You Choose?
Need gentle iron supplements or delicate etching? Pick FeCl₂. Want bold PCB traces, water treatment floc, or dramatic color tests? Go FeCl₃.
Can FeCl₂ become FeCl₃?
Yes, simply bubble air or add chlorine; the Fe²⁺ loses an electron and turns into Fe³⁺.
Is either form safe for home use?
Both can irritate skin and lungs; gloves, goggles, and good ventilation are mandatory.