Washing soda is:

Washing soda is chemically known as sodium carbonate decahydrate, represented by the chemical formula ${\text{Na}}_2{\text{CO}}_3\cdot 10{\text{H}}_2\text{O}$. In contrast, anhydrous sodium carbonate (${\text{Na}}_2{\text{CO}}_3$) is known as soda ash, and sodium bicarbonate (${\text{NaHCO}}_3$) is commonly referred to as baking soda.