Core Air & Water: Water
Slide 6 of 11
Chemical test for water
An alternative is to dip a cobalt chloride paper (or simply add anhydrous cobalt chloride crystals) to the liquid.
Dry (anhydrous) cobalt chloride CoCl2 is blue in color.
Cobalt Chloride is a deliquescent substance: it naturally attracts water molecules (CoCl2 ·xH2O).
 Hydrated cobalt chloride is pink in color.
The reaction is reversible: if the pink paper is dried after use it returns to being blue again.