NEW YORK (CNN/Money) - DuPont Co. posted sharply improved second-quarter earnings Wednesday that beat Wall Street's expectations, but the company warned it expects third-quarter results below current forecasts.

The chemical maker earned $711 million, or 71 cents a share, excluding special items, up from $432 million, or 41 cents a share, on the same basis a year earlier. Analysts surveyed by earnings tracker First Call had a consensus forecast of 66 cents.

Including special items the company had net income of $543 million, or 54 cents a share, compared with a net loss of $213 million, or 21 cents a share, a year before.

DuPont said it expects third-quarter earnings per share about double the underlying year-earlier 12 cents, well below First Call's forecast of 34 cents. The company said it expects fourth-quarter results about triple the 12 cents a share it earned in the fourth quarter of 2001, which is roughly in line with First Call's current 37-cents-a-share forecast.

The nation's No. 2 chemical company behind Dow Chemical said revenue fell to $6.7 billion from $7.2 billion a year earlier, which beat First Call's forecast of $6.4 billion.

Shares of DuPont (DD: Research, Estimates), a component of the Dow Jones industrial average, gained $1.82 to $38.87 Wednesday afternoon.