The owner of a Jersey City chemical company described in court Thursday how he had sold large quantities of the ingredients that the government says were used to make the bomb that exploded in the World Trade Center on Feb. 26.

Peter Wolpert, the president of the City Chemicals Corp. in Jersey City, provided a critical element in the complex web of circumstantial evidence that the prosecution is trying to spin around the four men on trial, which finished its seventh week of testimony Thursday.Wolpert said that he filled three large orders for urea, nitric acid, sulfuric acid and other chemicals that were placed by a man who identified himself as Kemal Ibraham. He then identified the man he knew as Kemal Ibraham as Ramzi Ahmed Yousef, using a photograph that had already been shown to the jury. Yousef was indicted in the trade center case but left the country the day of the explosion and has not been found since.

"I know him," Wolpert said, looking at the picture of a heavily bearded man. "He identified himself to me as Kemal."

While the jury has not yet heard testimony about the composition of the bomb that went off in the trade center, investigators have indicated that urea and nitric acid were among the most important ingredients. The prosecution presented evidence in previous days that three of the men on trial, Mohammed A. Salameh, Mahmud Abouhalima and Ahmad M. Ajaj, knew Yousef and had contacts with him in the months before the explosion.

Wolpert identified another man on trial, Nidal A. Ayyad, as having gone to City Chemical twice in attempts to pick up lead nitrate. Ayyad, who worked as a chemical engineer for the Allied-Signal Corp. in New Jersey, is accused of helping to purchase the chemicals used to make the bomb.

Wolpert's testimony followed another major piece of evidence presented Thursday by the assistant manager of a storage company in Jersey City where the chemicals from City Chemical were delivered. Joseph Moore, the assistant manager, said that he rented a 10-by-10-foot storage locker at Space Station Storage in Jersey City to a man who gave his name as Kemal Ibraham.

Moore was not asked to identify the man who actually went to the storage locker to sign the rental contract. But he said that two men used the locker two or three times a week, which he said was unusually often. He identified one of the men as Salameh, the lead defendant in the case. The indictment says that Salameh also used the alias Kemal Ibraham.

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