On heating `NaHCO_(3)` (baking soda), `CO_(2)` (carbon dioxide) gas is given out that turns lime water milky.
`2NaHCO_(3)overset(Heat)rarrNa_(2)CO_(3)+H_(2)O+cO_(2)uparrow`
While on heating `Na_(2)CO_(3).10H_(2)O`(washing soda) water of crystallisation is given out and the slat becomes anhydrous. The presence of water of crystallisation given as p[roduct can be tested by treating it with anhydrous `CuSO_(4)` (white) which becomes blue in colour in its contact.
`Na_(2)CO_(3).10H_(2)Ooverset(Heat)rarrNa_(2)CO_(3)+10H_(2)O`
