Identifying Hydrogen Minerals

Closed Tube Test for Water. Hydrogen exists in minerals either as water of crystallization (for example, gypsum, CaSO₄.- 2H₂O) or as the hydroxyl radical (for example, brucite, Mg (OH)₂). In either case its presence may be detected by heating a fragment of the mineral in a closed tube and observing the water which condenses upon the upper cold wall of the tube. Water of crystallization is driven off more readily than water of hydroxyl, but the test is easily obtained in either case.