The Chemist's War: The little-told story of how the U.S. government poisoned alcohol during Prohibition with deadly consequences, by Deborah Blum (Slate)
... Frustrated that people continued to consume so much alcohol even after it was banned, federal officials had decided to try a different kind of enforcement. They ordered the poisoning of industrial alcohols manufactured in the United States, products regularly stolen by bootleggers and resold as drinkable spirits. The idea was to scare people into giving up illicit drinking. Instead, by the time Prohibition ended in 1933, the federal poisoning program, by some estimates, had killed at least 10,000 people.
Although mostly forgotten today, the "chemist's war of Prohibition" remains one of the strangest and most deadly decisions in American law-enforcement history. As one of its most outspoken opponents, Charles Norris, the chief medical examiner of New York City during the 1920s, liked to say, it was "our national experiment in extermination."
The big enforcement issue during Prohibition was stolen industrial alcohol. The denaturing formula is hard reading, indeed.
To sell the stolen industrial alcohol, the liquor syndicates employed chemists to "renature" the products, returning them to a drinkable state. The bootleggers paid their chemists a lot more than the government did, and they excelled at their job. Stolen and redistilled alcohol became the primary source of liquor in the country. So federal officials ordered manufacturers to make their products far more deadly.
By mid-1927, the new denaturing formulas included some notable poisons—kerosene and brucine (a plant alkaloid closely related to strychnine), gasoline, benzene, cadmium, iodine, zinc, mercury salts, nicotine, ether, formaldehyde, chloroform, camphor, carbolic acid, quinine, and acetone. The Treasury Department also demanded more methyl alcohol be added—up to 10 percent of total product. It was the last that proved most deadly.