Ethyl Anti-Knock Gas
After General Motors scientists discovered the anti-knock properties of tetraethyl lead gasoline in 1921, American motorists will be saying, “Fill ‘er up with Ethyl.”
In early internal combustion engines, “knocking” resulted from the out-of-sequence detonation of the gasoline-air mixture in a cylinder. The constant shock added to exhaust valve wear and frequently damaged engines.
After five years of lab work to find an additive to eliminate pre-ignition “knock” problems of gasoline, General Motors researchers Thomas Midgely Jr. and Charles Kettering discovered the anti-knock properties of tetraethyl lead. Their early experiments had examined the properties of knock suppressors such as bromine, iodine and tin – and compare these to new additives such as arsenic, sulfur, silicon and lead.
On December 9, 1921, when the two chemists synthesized tetraethyl lead and tried it in their one-cylinder laboratory engine, the knocking abruptly disappeared and fuel economy improved. “Ethyl” vastly improved gasoline performance.
Although being diluted to a ratio of one part per thousand, the lead additive yielded gasoline without the loud, power-robbing knock. With GM scientists watching, the first car tank filled with leaded gas took place on February 2, 1923, at the Refiners Oil Company service station in Dayton, Ohio. GM provided Refiners Oil Company and other service stations simple bolt on adapters called “Ethylizers” to meter the proper proportion of the new additive.
“By the middle of this summer you will be able to purchase at approximately 30,000 filling stations in various parts of the country, a fluid that will double the efficiency of your automobile, eliminate the troublesome motor knock, and give you 100 percent greater mileage,” Popular Science Monthly reported in 1924.
Anti-knock gasoline containing a tetraethyl lead compound also proved vital for aviation engines during World War II, even as danger from the lead content increasingly became apparent.
Powering Allied Victory in World War II
Aviation fuel technology was still in its infancy in the 1930s. The properties of tetraethyl lead proved vital to the Allies during World War II.
Advances in aviation fuel increased power and efficiency, resulting in the production of 100-octane aviation gasoline shortly before the war.
Phillips Petroleum – today’s ConocoPhillips – was involved early in aviation fuel research and had already provided high gravity gasoline for some of the first mail-carrying airplanes after World War I.
Phillips Petroleum produced aviation fuels before it produced automotive fuels. The company’s gasoline came from the high-quality oil produced during the Osage County oil boom, which began in 1917.
Although today still an ingredient of 100 octane “avgas” for piston-engine aircraft, tetraethyl’s danger to public health was underestimated for decades.
Tetraethyl lead’s Deadly Side
Leaded gasoline was extremely dangerous from the beginning, according Deborah Blum, a Pulitzer-Prize winning science writer.
“G.M. and Standard Oil had formed a joint company to manufacture leaded gasoline, the Ethyl Gasoline Corporation,” she notes in a 2011 article. Research focused solely on improving the formula, not on the danger of the lead additive.
“The companies disliked and frankly avoided the lead issue,” Blum writes in “Looney Gas and Lead Poisoning: A Short, Sad History” at Wire.com. “They’d deliberately left the word out of their new company name to avoid its negative image.”
In 1924, dozens were sickened and five employees of the Standard Oil Refinery in Bayway, New Jersey, died after they handled the new gasoline additive.
In May 1925, the U.S. Surgeon General called a national tetraethyl lead conference, Blum says, and an investigative task force was formed. Researchers concluded there was ”no reason to prohibit the sale of leaded gasoline” as long as workers were well protected during the manufacturing process.
So great was the additive’s potential to improve engine performance, the author notes, by 1926 the federal government approved continued production and sale of leaded gasoline. “It was some fifty years later – in 1986 – that the United States formally banned lead as a gasoline additive,” Blum adds.
In the 1950s, geochemist Clair Patterson discovered the toxicity of tetraethyl lead; phase-out of its use in gasoline began in 1976 and was completed by 1986. In 1996, EPA Administrator Carol Browner declared, “The elimination of lead from gasoline is one of the great environmental achievements of all time.”
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