Soda extract is useful when given mixture has any insoluble salt, it is prepared by :

Soda extract is useful when the given mixture has any insoluble salt, it is prepared by boiling ${\mathrm{Na}}_2{\mathrm{CO}}_3$ and mixture in distilled water.
To make soda extract, combine 12 g of salt combination with 5–6 g of anhydrous ${\mathrm{Na}}_2{\mathrm{CO}}_3$  and 10 ml of water, and stir to dissolve. Heating, filtration, washing, and analysis are done after the mixing. Soda extract is made for examination if the provided salt combination is partially soluble or insoluble in water.