For anhydrous salt

$\begin{array}{ccccccccc}\text{Element}& & \text{Al} & & \text{K}& & \text{S}& & \text{O}\\ \text{Atomic ratio}& & \frac{10·5}{27}& & \frac{15·1}{39}& & \frac{24·8}{32}& & \frac{49·6}{16}\\ & & 0·39& & 0·39& & 0·78& & 3·10\end{array}$

Empirical formula of anhydrous salt = KAlS₂O₈

E.F mass of Anhydrous salt = 258 g/mol

Mass of Moisture $=258\times \frac{45·6}{54·4}=216\text{ g}$

$=\frac{216}{18}\approx 12\text{ mole}$

Empirical formula of Anhydrous salt KAlS₂O₈.12H₂O

$\text{E F}\text{ Mass}=258+216=474$ g/Empirical formula mass

$\text{n}=\frac{\text{Mole Mass}}{\text{E.F. Mass}}=\frac{948}{474}=2$

Molecular Formula = K₂Al₂S₄O₁₆.24H₂O
 
                            = K₂SO₄.Al₂(SO₄)₃.24H₂O