Baking soda is not used in _______.

Baking soda is a very important compound obtained from common salt. It is used all around in our daily life. Due to its basic nature, it is used as an Antacid in medicine to remove the acidity of the stomach. It is used in making baking powder which is used for baking. On reacting with acids it produces carbon dioxide gas which does not support combustion and therefore, is used as a fire extinguisher. It can not be used in removing the permanent hardness of water as it does not have the capacity to form soluble compounds with the calcium and magnesium ions present in the hard water.