Weak car production and lower metals prices earlier this year took their toll on platinum refiner Johnson Matthey's first half, though it expects an improvement over the rest of the year.Pre-tax profits dropped 22% to £109.5m in the half year to September. Sales fell 18% at £3.6bn as a result of reduced activity and lower precious metal prices. Stripping out the impact of precious metals, sales were down 5% at £883m."Johnson Matthey performed well in the first half of 2009/10 despite a 16% drop in global light duty vehicle production and a 33% reduction in the average price of platinum," chief executive Neil Carson said.Going forward, the second half is tipped to see the core Environmental Technologies Division, which produces vehicle exhaust catalysts, "signficantly up" compared with the same time last year. Results in the Precious Metal Products are expected to improve further, though are unlikely to match those for the second half of last year Fine Chemicals is expected to deliver steady underlying growth for the full year if the one-off benefit associated with the launch of Adderall XR is excluded.The interim dividend is maintained at 11.1p.