Although first-half revenue dropped by a quarter at Johnson Matthey after the loss of a major contract with Anglo American Platinum (Amplats), the chemical and sustainable technologies group lifted its dividend by 9% after profits improved.The FTSE 100 company also lifted its full-year guidance slightly, predicting that foreign exchange movements would not have a major impact on second-half results.Revenue totalled £4.8bn in the six months to 30 September, down 25% on a reported basis, mainly owing to a 32% drop in revenue at the precious metals (PMP) division. At constant exchange rates, group revenues would have been 22% than the previous year.The company said it made "good progress" during the half, "notwithstanding the effect of foreign currency translation and the loss of commission revenue from [Amplats]". Sales excluding precious metal sales increased by 2% to £1.5bn.Group underlying pre-tax profit totalled £216.4m, up 2% on last year and 10% higher at constant exchange rates. The interim dividend was lifted to 18.5p per share, from 17p a year earlier.Johnson Matthey hailed the performance of its emission control technologies (ECT) division, which grew revenues 21% due to tightening legislation in Europe and Asia and good demand for heavy duty diesel trucks in the US.Chief executive Robert MacLeod said the first-half performance was in line with expectations and good underlying growth is expected in the second half."If current exchange rates prevail, foreign currency translation will not materially impact results in the second half. The group's performance in 2014/15 is expected to be slightly ahead of 2013/14."This compares with previous guidance of a "broadly in line" result compared with last year. The company had said as recently as July that exchange rates at the time, if sustained over the full year, would have reduced underlying operating profit by over £25m.