Washing Soda (Sodium Carbonate)

In domestic use, sodium carbonate (washing soda) is used as a water softener in laundering. It competes with the magnesium and calcium ions in hard water and prevents them from bonding with the detergent being used. Sodium carbonate can be used to remove grease, oil and wine stains. Sodium carbonate is also used as a descaling agent in boilers such as those found in coffee pots and espresso machines.

In dyeing with fibre-reactive dyes, sodium carbonate (often under a name such as soda ash fixative or soda ash activator) is used to ensure proper chemical bonding of the dye with cellulose (plant) fibres, typically before dyeing (for tie dyes), mixed with the dye (for dye painting), or after dyeing (for immersion dyeing).