When Carol Ann Bond, a Rohm & Haas chemical technician in Montgomery County, discovered that her husband had fathered a child with another woman, she drew upon her training to retaliate.

She laced the other woman's front door, car and mailbox with chemicals she obtained from work and the Internet, according to her guilty plea in federal court yesterday.

The other woman, Myrlinda Haynes, was not injured during the attacks, which began on Thanksgiving 2006 and ended in May, but she immediately suspected Bond and called U.S. postal inspectors.

The inspectors set up a video camera in Haynes' home to try to catch Bond in the act. They did, taping her stealing mail and putting red powder on Haynes' car door and tailpipe.

Inspectors identified the chemicals as potassium dichromate and chloro-phenoxarsine. In a filing, the government said that "if potassium dichromate is ingested, it may cause severe burns of the mouth, throat and stomach, leading to death."

The government said absorption of chloro-phenoxarsine "through the skin may be fatal."

The inspectors learned that 4 pounds of potassium dichromate was missing from Rohm & Haas' offices in Spring House, where Bond worked from 2000 to 2006, and which she left on good terms. They also traced the chloro-phenoxarsine to Rohm & Haas.

Yesterday, Bond pleaded guilty to the federal crime of "use of a chemical weapon." She admitted to taking some of the chemicals from work and buying others over the Internet.

U.S. District Judge James T. Giles set sentencing for March 19. The federal advisory guidelines call for a sentence of about five years, Assistant U.S. Attorney Amy L. Kurland said.

Bond's lawyer, Robert Goldman, had argued that the statute was unconstitutional and had been misapplied in the case. He said Bond's plea showed that she took responsibility for her conduct.

"She's well respected by her family, coworkers, neighbors and friends," he said yesterday, noting that she had a new job in California. "Obviously, something broke inside her, psychologically. And we're trying to get to the bottom of it in order to present to the court at sentencing."