Heating an aqueous solution of aluminium chloride to dryness will give:

When an aqueous solution of ${\text{AlCl}}_3$ is heated, hydrolysis occurs. Because ${\text{Al}}^{3+}$ is a small, highly charged cation, it strongly attracts water.Heating the hydrated salt (${\text{AlCl}}_3\cdot 6{\text{H}}_2\text{O}$) causes it to lose $\text{HCl}$ gas instead of just water:
$$2[{\text{Al(H}}_2{\text{O)}}_6]{\text{Cl}}_3\stackrel{\Delta }{\to }{\text{Al}}_2{\text{O}}_3+6\text{HCl}+9{\text{H}}_2\text{O}$$
The final solid residue is alumina (${\text{Al}}_2{\text{O}}_3$).