Jordan first to reach 50 Championship wickets
Sussex 314 and 11 for 1 lead Derbyshire 274 (Madsen 97, Jordan 3-73) by 51 runs
Sussex all-rounder Chris Jordan became the first man to reach 50 Championship wickets for the season to maintain the impetus in their title challenge on the second day of the Division One game against Derbyshire at Hove.
Jordan reached the landmark when he had Tim Groenewald well caught by Michael Yardy at second slip to give him his third wicket of the day.
Derbyshire, still looking for their first win of the season, were made to battle hard for runs, even though the ball did not swing as generously as it did on the opening day. They were bowled out for 274, conceding a first innings lead of 40 runs.
At stumps Sussex had extended their lead to 51, although they did lose Chris Nash who was bowled by Groenewald just before the close.
Derbyshire's captain Wayne Madsen was the only specialist batsman to offer strong resistance, batting four minutes short of four hours for 97 but there was valuable support lower down the order from Peter Burgoyne, who scored his maiden Championship fifty in only his second match.
Burgoyne, 19, went to Zimbabwe with Derbyshire's batting coach Dave Houghton in the winter and scored two first-class hundreds and he and Madsen briefly gave the visitors a period of ascendancy.
Sussex, looking for their fifth win of the season, took their first wicket of the morning when Jordan had Chesney Hughes caught behind for 16. Three overs later Steve Magoffin had Ben Slater caught behind for 16.
Luke Wright, operating off a shortened run, appeared to be the least threatening of the Sussex bowlers but he put his side well on top with two quick wickets. First, he had Shivnarine Chanderpaul brilliantly caught by Jordan, low to his left at first slip, and then dismissed Richard Johnson, who played a weak shot to short cover.
When Jordan had Alex Hughes - making his first-class debut - caught at short leg Derbyshire were in trouble at 103 for five.
But Madsen led the recovery, first adding 36 with Tom Poynton and then 78 with Burgoyne, who finished unbeaten on 62 from 105 balls, with eight fours and a six. Madsen was seventh out at 217, missing out on his hundred as he was lbw to Monty Panesar, playing to leg.
Groenewald was eighth out to give former Surrey man Jordan his landmark and then Matthew Higginbottom, on his Championship debut, was bowled for nine. Ed Joyce ran out last man Mark Footitt for six but Derbyshire struck a late blow by dismissing Nash before Luke Wells and nightwatchman Lewis Hatchett saw their side through to stumps.