The molar mass of Al2(S2O3)3 is 342.15 g/mol. So, 25.6 g of Al2(S2O3)3 is 25.6 g / 342.15 g/mol = 0.0748 mol.

Each mole of Al2(S2O3)3 contains 3 moles of sulfur atoms. So, 0.0748 mol of Al2(S2O3)3 contains 3 * 0.0748 mol = 0.224 mol of sulfur atoms.

Therefore, 25.6 g of Al2(S2O3)3 contains 0.224 mol of sulfur atoms.