The mineral petalite was discovered by Jos Bonifcio de Andrada e Silva at Ut Mines. Petalite has

The mineral petalite was discovered by José Bonifácio de Andrada e Silva at Utö Mines. Petalite has the chemical formula XAlSi₄O₁₀ where X is an alkali metal. From 1g of petalite, Arfwedson received 0.96g SiO₂ + Al₂O₃. After the addition of H₂SO4, Arfwedson received 0.147 g of X₂SO_4. Use the atomic weights of Na (23), Li (7), S (32) and O (16) and Arfwedson's measurements to calculate the mass of X₂O in petalite if X is i) Na and ii) Li.