The death of Linda Riss Pugach, who was blinded in one eye from a lye attack ordered by her lover and eventual husband Burt Pugach, has piqued the curiosity of Internet users who are wondering: What is lye?

Also known as caustic soda, the chemical term for lye is sodium hydroxide, a dangerous substance that causes blindness when applied to the eyes.

Lye is colorless when applied on a white object and is odorless as a solid – whether it is in flake, bead or granular form, according to the Centers for Disease Control’s Pocket Guide To Chemical Hazards.

While lye was harmful in the case of Linda Pugach, who was blinded by the chemical, the substance also has helpful uses. Lye is used in the making of soap and can be purchased by those interested in making their own at websites such as AAA Chemicals, a company that sells lye to aid in making homemade soap.

But even though lye has non-sinister uses, the chemical is still dangerous. If lye is inhaled, ingested or makes contact with your eyes or skin, the substance can cause a number of unsettling symptoms, according to the CDC. Those symptoms include irritation to the eyes, skin and mucous membranes, eye and skin burns and temporary hair loss.

Quick first aid can help reduce the harmful effects of lye exposure, the agency says in its pocket guide, including flushing skin with water and irrigating the eyes.

PPG Industries, a lye supplier, warns its customers about the dangers of caustic soda.

“Caustic soda (also called lye or sodium hydroxide) attacks the skin and eyes rapidly. Even a small quantity of a dilute solution can severely injure the eyes or cause blindness. Overexposure to caustic soda by way of skin burns or swallowing can cause death,” the company cautions.

Pugach went blind in one eye after her then-lover and eventual husband, Burt Pugach, ordered men to frighten her in 1959 after she decided to call off their affair. She died Tuesday night at age 75 after suffering from rheumatic fever.

Yet, she went on to marry Burt Pugach, and their bizarre love story was the subject of the 2007 documentary “Crazy Love.”

“We had a fairy tale marriage,” a grief stricken Burt Pugach told the New York Daily News. “She was extremely loyal to me … I don’t know how I’m going to be able to continue without her.”

He served 14 years in prison for his role in the lye attack. Pugach hired three men to “frighten” his mistress, and he denied ordering them to use the lye to blind her, the New York Times said.

“I asked one guy to find someone who would beat her up, to try and get her back,” he told the newspaper. “I didn’t ask anybody to throw lye at her.”

Dan Klores, director of “Crazy Love,” said the relationship between Burt and Linda Pugach “was on some level tragic, but also psychologically fulfilling.”

The couple’s story made tabloid headlines in New York in the 1970s, and a book about their love, “A Very Different Love Story,” was published in 1976, an article in the New York Times said.

Burt Pugach told the newspaper that he and his wife spent the time after the attack declaring their love for each other in the media.

“We loved each other more than any other couple could have,” he said. “Ours was a storybook romance.”

Twenty years after the attack, the couple’s marriage was in the limelight again when Burt Pugach was on trial for alleged sexual abuse and threatening to kill a woman who he had been carrying on an affair with for five years while still married to Linda Pugach.

Linda Pugach testified during the 1997 trial and supported her husband, who was convicted of harassment but acquitted on more serious charges. Burt Pugach was sentenced to 15 days in jail in the case.

“You’re a wonderful, caring husband,” she testified, the New York Times quoted her as saying at the time.

Linda Pugach was viewed by some as an Elizabeth Taylor look-alike, and Klores said she suffered after the lye attack.

"She was a sheltered, naïve young girl,” he told the Times. “Her identity was centered around her physical beauty. When she had this romance with this older man — this obsessive relationship — he worshiped her for that physical beauty. And when that was taken from her, the scars weren’t merely on the outside.”