Washing soda is prepared by sodium carbonate by adding 10 molecules of water of crystallization to each formula unit and is also known as sodium carbonate decahydrate or washing soda.\\\\(\\underset{Sodium \\\\ Carbonate}{Na_2CO_3} + 10H_2O \\longrightarrow \\underset{washing \\ soda}{ Na_2CO_3. 10H_2O}\\\\)Washing soda is a sodium salt that is basic nature.Washing soda can be used to remove both temporary and permanent hardness in water. It is soluble in water and adds a large amount of carbonate ions in the water. These react with dissolved calcium and magnesium ions to produce insoluble precipitates. Sodium carbonate is soluble but calcium carbonate and magnesium carbonate are insoluble.