Metallurgy

Let's analyze each option in terms of whether it contains water of crystallization or is associated with water molecules:
Cryolite ( Na3AlF6 )
→ This compound does not contain water molecules. It is anhydrous (no water of crystallization).
✓ Not associated with water molecules.
Bauxite (Al2O3⋅×H2O)
→ This is a hydrated form of alumina, i.e. it does contain water molecules.
- Associated with water.
Kernite (Na2B4O7⋅4H2O)
→ This is hydrated sodium borate, contains crystallization water.
- Associated with water.
Borax (Na2B4O7⋅10H2O )
→ This also contains crystal water.
- Associated with water.
Correct Answer: Option A - Cryolite
Reason: Cryolite (Na3AlF6) is not associated with water molecules.