Washing soda is a compound of sodium, carbon and oxygen, bound together as sodium carbonate. A common source of sodium carbonate is the ashes of plants. Another source is sodium chloride, or table salt.
Washing soda, also known as sodium carbonate, is similar to baking soda, or sodium bicarbonate. Sodium carbonate is highly alkaline and binds to minerals to remove stains, soften hard water and allow detergent to foam and rinse out of clothes. Sodium carbonate does not stain or bleach clothes. It can also descale bathroom tiles and coffee machines, scrub stoves and strip floors of wax. Sodium carbonate can irritate skin, eyes and lungs if inhaled.