The Secret History of Lead
The Search for an Antiknock
On December 9, 1921, a young engineer named Thomas Midgley Jr., working in the laboratory of the General Motors Research Corporation in Dayton, Ohio, reported to his boss, Charles Kettering, that he'd discovered that tetraethyl lead--a little-known compound of metallic lead and one of the alkyl series, also referred to as lead tetraethyl or TEL--worked to reduce "knock" or "pinging" in internal-combustion engines.
Tetraethyl lead was first discovered by a German chemist in 1854. A technical curiosity, it was not used commercially on account of "its known deadliness." It is highly poisonous, and even casual cumulative contact with it was known to cause hallucinations, difficulty in breathing and, in the worst cases, madness, spasms, palsies, asphyxiation and death. Still unused in 1921, sixty-seven years after its invention, it was not an obvious choice as a gasoline additive.
In the laboratories of Charles Kettering, however, the search for a gasoline additive to cure "knock" had been going on for some years prior to Midgley's rediscovery of TEL. In 1911 Kettering had invented the electric self-starter--a landmark development in automotive history that eliminated dangerous hand-cranking and enabled many Americans (particularly women) to drive for the first time, arguably killing steam and electric cars in the process. This invention would make "Boss" Kettering rich, famous and beloved to a nation falling in love with its wheels. Thanks to the starter, the folksy inventor's new firm, Dayton Engineering Laboratories Company, or DELCO, received its first big order, for $10 million, from the upstart General Motors Corporation, founded only three years earlier by William Crapo Durant.
GM's 1912 Cadillac was equipped with DELCO's self-starter and battery ignition. When customers reported that the engine of this luxury automobile had an alarming tendency to knock--a sharp, metallic sound hinting at damage being done inside the engine--critics blamed Kettering's electrical components.
Kettering was convinced, rightly, that knocking was a function of an engine's fuel rather than ignition problems. When Kettering and his partners sold DELCO to Durant's GM and its new partner--Alfred Sloan's Hyatt Roller Bearings--in 1916, his lab was already engaged in a search for the cure. Following the sale, this work was transferred to his new firm, the Dayton Research Laboratories, where a newly hired assistant, Thomas Midgley, was assigned to study the problem of engine knock.
Stabbing in the dark, Midgley got lucky quickly when he added iodine to the fuel, stopping knock in a test engine and establishing for all time that the malady--premature combustion of the fuel/air mixture--was connected to the explosive qualities of the fuel, what would later be called "octane." Iodine raised octane and cured knock; however, it was corrosive and prohibitively expensive. Inspired by the fundamental breakthrough, Midgley nonetheless carried on with fuel research, testing every substance he could find for antiknock properties, "from melted butter and camphor to ethyl acetate and aluminum chloride." Unfortunately, "most of them had no more effect than spitting in the Great Lakes."
The Antiknock That Got Away
Automotive engineers knew by this time that engines that didn't knock would not only operate more smoothly. They could also be designed to run with higher compression in the cylinders, which would allow more efficient operation, resulting in greater fuel economy, greater power or some harmonious combination of the two. The key was finding a fuel with higher octane. Though octane sufficient for use in high-compression engines had been achievable since 1913 through a process called thermal cracking, the process required added expenditures on plant and equipment, which tightfisted oil refiners didn't relish. The nation's fuel supply remained resolutely low grade, a situation that troubled Kettering.
By limiting allowable compression, low-octane fuel meant cars would be burning more gasoline. Like many visionary engineers, Kettering was enamored of conservation as a first principle. As a businessman, he also shared persistent fears at the time that world oil supplies were running out. Low octane and low compression meant lower gas mileage and more rapid exhaustion of a dwindling fuel supply. Inevitably, demand for new automobiles would fade.
By 1917 Kettering and his staff had trained their octane-boosting sights on ethyl alcohol, also known as grain alcohol (the kind you drink), power alcohol or ethanol. In tests supervised by Kettering and Midgley for the Army Air Corps at Wright Field in Dayton, Ohio, researchers concluded that alcohols were among the best antiknock fuels but were not ideal for aircraft engines unless used as an additive, in a blend with gasoline. This undoubtedly led Kettering to concur with an April 13, 1918, Scientific American report: "It is now definitely established that alcohol can be blended with gasoline to produce a suitable motor fuel."