2. In this Act, unless the context otherwise requires —
“Controller” means the Controller appointed by the President under section 3;
“smelter” includes a person who keeps any factory or place for the purpose of smelting or otherwise treating tin or tin-ore;
“treat”, with its grammatical variations, means to subject to any process whereby chemical or physical change takes place in the substance subjected thereto;
“tin-ore” shall be deemed to include any mineral or admixture of minerals containing more than 4% of metallic tin.