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Chemistry LibreTexts

1: Tetraethyllead: Kettering and Midgley

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  • Charles F. Kettering, was a leading researcher for the automotive industry. His early contribution of the battery powered electric starter relieved all of us of the troublesome and dangerous operation of cranking the automobile to start it. His Dayton Metal Products Co. was merged with General Motors in 1919 and became the core of GM's research division. Kettering’s later fuel research had opened two very interesting doors to solve the problems of poor quality resulting from insufficient supply and the need for high compression engines.

    The great Institutes Kettering founded and the many admirers of Charles Kettering's (1876-1958) fine mind and diligent work have given us a wide variety of public sources about his life and thinking. See:

    • A brief biography accompanying his introduction into the Inventors Hall of Fame.
    • A biography from the Kettering University named in his honor.
    • A list of his inventions at a site for a medical center he funded.
    • The cancer Institute he helped originate.
    • The Foundation that deals with our democratic processes


    His high percentage solutions – alcohol and benzene -- “appear to be very promising allies” to petroleum, Kettering’s assistants Thomas Midgley and T.A. Boyd said..[i] Alcohol was the “most direct route ... for converting energy from its source, the sun, into a material that is suitable for a fuel...” But alcohol from food crops involved supply problems. Only celluosic biomass had the potential to compete with petroleum over the long run, they believed

    Thomas Midgley, Jr.

    The second door -- the“low percentage class” of solution -- was originally represented by iodine. It was far too expensive to be practical, but it led to experiments in 1920 and 1921 that would change the automotive world.

    The experiments were guided by a peg board with a portion of the periodic table of elements pasted on it. The board helped the researchers compare their tests of already known knock suppressors (such as bromine, iodine, tellurium, tin and selenium) and new fuel additives (such as arsenic and sulfur). Historians have seen it as a beautiful piece of pure research.

    The atmosphere in the labs grew more expectant as the pegboard seemed to point the way toward the heavy end of the carbon group: silicon, germanium, tin and lead. Visiting his father in Massachusetts in late October, Midgley had antiknock results from each new test sent via telegraph daily. Tetraethyl tin proved effective, but even more exciting was the prospect of metallic lead at the bottom of the column on the peg board.

     When the chemists finally delivered a small amount of tetraethyl lead on the morning of December 9, 1921, the knock in the one-cylinder laboratory engine was utterly silenced. Even diluted to a strength of two or three grams per gallon, or one thousand to one, tetraethyl lead had a remarkable ability to quiet the relentless knocking.

    But Midgley and Kettering’s interest in ethyl alcohol fuel did not fade once tetraethyl lead was discovered as an antiknock in December, 1921. In fact, not only was ethyl alcohol a source of continued interest as an antiknock agent, but more significantly, it was still considered to be the fuel that would eventually replace petroleum. A May, 1922 memo from Midgley to Kettering was a response to a report on alcohol production from the Mexican "century" plant, a desert plant that contains fermentable sugars. Midgley said he was "not impressed" with the process as a way to make motor fuel: 

    Unquestionably alcohol is the fuel of the future and is playing its part in tropical countries situated similar [sic] to Mexico. Alcohol can be produced in those countries for approximately 7 - 1/2 cents per gallon from many other sources than the century plant, and the quantities which are suggested as possibilities in this report are insignificantly small compared to motor fuel requirements. However, as a distillery for beverage purposes, these gentlemen may have a money making proposition.[i]

    Even as chemists tinkered with various processes to produce tetraethyl lead in a nearby lab, Midgley and Boyd continued working on alcohol for fuel. In a June 1922 Society of Automotive Engineers paper, they said: 

    That the addition of benzene and other aromatic hydrocarbons to paraffin base gasoline greatly reduces the tendency of these fuels to detonate [knock] ... has been known for some time. Also, it is well known that alcohol ... improves the combustion characteristics of the fuel ...The scarcity and high cost of gasoline in countries where sugar is produced and the abundance of raw materials for making alcohol there has resulted in a rather extensive use of alcohol for motor fuel. As the reserves of petroleum in this country become more and more depleted, the use of benzene and particularly of alcohol in commercial motor fuels will probably become greatly extended.” [ii] (Italics indicate section omitted from printed version).

    In September, 1922, Midgley and Boyd wrote that “vegetation offers a source of tremendous quantities of liquid fuel.” Cellulose from vegetation would be the primary resource because not enough agricultural grains and other foods were available for conversion into fuel. “Some means must be provided to bridge the threatened gap between petroleum and the commercial production of large quantities of liquid fuels from other sources. The best way to accomplish this is to increase the efficiency with which the energy of gasoline is used and thereby obtain more automotive miles per gallon of fuel.”[iii] At the time the paper was written, in late spring or early summer 1922, tetraethyl lead was still a secret within the company, but it was about to be announced to fellow scientists and test marketed. The reference to a means to "bridge the threatened gap" and increase in the efficiency of gasoline clearly implies the use of tetraethyl lead or some other additive to pave the way to new fuel sources.

    This inference is consistent with an important statement in an unpublished 1936 legal history of Ethyl Gasoline for the du Pont corporation: 

     It is also of interest to recall that an important special motive for this [tetraethyl lead] research was General Motors’ desire to fortify itself against the exhaustion or prohibitive cost of the gasoline supply, which was then believed to be impending in about twenty-five years; the thought being that the high compression motors which should be that time have been brought into general use if knocking could be overcome could more advantageously be switched to [ethyl] alcohol. [iv]

     Thus, during the time Kettering and Midgley researched anti-knock fuels (1916 to 1925), and especially after tetraethyl lead was discovered in December of 1921, there were two “ethyls” on the horizon for General Motors: Ethyl leaded gasoline, which would serve as a transitional efficiency booster for gasoline, and ethyl alcohol, the "fuel of the future" that would keep America’s cars on the roads no matter what happened to domestic or world oil supply. Thus, Kettering's strategy in the post World War I years was to prepare cars for high-octane alternative fuels if needed.


    1. [i] Midgley to Kettering, May 23, 1922, Factory Correspondence, Midgley unprocessed files, GMI. 
    2. [ii] Thomas A. Midgley and T.A. Boyd, “Detonation Characteristics of Some Blended Motor Fuels,” SAE Journal, June 1922, page 451. Note: italics indicate a section used at the oral presentation at a June 1922 SAE meeting but not published in the SAE paper; oral presentation from Midgley unprocessed files, GMI. 
    3. [iii] Thomas Midgley and Thomas Boyd, “The Application of Chemistry to the Conservation of Motor Fuels,” Industrial and Engineering Chemistry, Sept. 1922, p. 850.
    4. [iv] N. P. Wescott, Origins and Early History of the Tetraethyl Lead Business, June 9, 1936, Du Pont Corp. Report No. D-1013, Longwood ms group 10, Series A, 418-426, GM Anti-Trust Suit, Hagley Museum & Library, Wilmington, Del., p. 4.

    The Eureka Moment

    We wrote briefly about practical scientific research. This can be a series of experiments based on a plan, but without a true scientific hypothesis. Kettering and Midgley scouted through the periodic table of the elements and as they neared the bottom - the heavier elements - they began to see a pattern. They could predict that tetraethyllead might well be the chemical compound they sought for protection against knocking - and it was.

    This moment when we can laugh and say "Eureka" comes only so often in the life of a scientist - and only after years of toil and effort!