Al-Al2(SO4)3-> Al(OH)3-> AlCl3->Na[Al(OH)4]

2Al + 3H2SO4 = Al2(SO4)3 + 3H2Al2(SO4)3 + 6NaOH = 2Al(OH)3 + 3Na2SO4Al(OH)3 + 3KCl = AlCl3 + 3KOHAlCl3 + 4NaOH(k.) = Na[Al(OH)4] + 3NaCl