2850 Hydrides, nitrides, azides, silicides and borides, whether or not chemically defined (excl. compounds which are also carbides of heading 2849, and inorganic or organic compounds of mercury whether or not chemically defined)
2850 Hydrides, nitrides, azides, silicides and borides, whether or not chemically defined (excl. compounds which are also carbides of heading 2849, and inorganic or organic compounds of mercury whether or not chemically defined)