Chemical firm Johnson Matthey has agreed to sell its gold and silver refining business to Asahi Holdings for £118m in cash.The business, based in the US and Canada, refines primary and secondary gold and silver materials and reported sales of £44m in the financial year ended 31 March."The divestment of the gold and silver refining business is in line with our long-term strategy to focus on areas where we can use our expertise in chemistry and its applications," said group chief executive Robert MacLeod.The group expects the transaction to complete by the end of March 2015.