E tan 1 phần chứng tỏ E có cả Cu và $Al_2O_3$.
$2Na+2H_2O\to 2NaOH+H_2$
$Al_2(SO_4)_3+6NaOH\to 2Al(OH)_3+3Na_2SO_4$
$CuSO_4+2NaOH\to Cu(OH)_2+Na_2SO_4$
$Al(OH)_3+NaOH\to NaAlO_2+H_2O$
$Cu(OH)_2\buildrel{{t^o}}\over\to CuO+H_2O$
$2Al(OH)_3\buildrel{{t^o}}\over\to Al_2O_3+3H_2O$
$CuO+H_2\buildrel{{t^o}}\over\to Cu+H_2O$
$Al_2O_3+6HCl\to 2AlCl_3+3H_2O$