错误:
KCN %2B FeSO4 %2B KOH %3D K4Fe%28CN%296 %2B Fe%28OH%292 %2B K2SO4
^不需要的字符 ('%')KCN %2B FeSO4 %2B KOH %3D K4Fe%28CN%296 %2B Fe%28OH%292 %2B K2SO4
^不需要的字符 ('%')