1. For the purpose of sub-heading 2620 21, "leaded gasoline sludges and leaded antiknock compound sludges” mean sludges obtained from storage tanks of leaded gasoline and leaded anti-knock compounds (for example, tetraethyl lead), and consisting essentially of lead, lead compounds and iron oxide.

2. Slag, ash and residues containing arsenic, mercury, thallium or their mixtures, of a kind used for the extraction of arsenic or those metals or for the manufacture of their chemical compounds, are to be classified in sub-heading 262060.