${\mathrm{K}}_2{\mathrm{SO}}_4.{\mathrm{Al}}_2{\left({\mathrm{SO}}_4\right)}_3. 24{\mathrm{H}}_2\mathrm{O}$ is

${\mathrm{K}}_2{\mathrm{SO}}_4$ = potassium sulfate 
${\mathrm{Al}}_2{\left({\mathrm{SO}}_4\right)}_3$= aluminum sulfate 
${\mathrm{H}}_2\mathrm{O}$= water 
This substance contains two salts. A salt known as a double salt, such as carnallite, is one that crystallizes as a single material but dissolves as two distinct salts when ionized. Thus dissolves as ${\mathrm{K}}_2{\mathrm{SO}}_4, {\mathrm{Al}}_2{\left({\mathrm{SO}}_4\right)}_3$ dissolves as potassium sulfate, and aluminium sulfate is its constituent salt with its own distinct lattice structure.