3: Tetraethyllead - Additives

Most fuel research within the oil industry involved new ways to create branched chain hydrocarbons in the less volatile fractions of the fuel. Oil industry researchers found that if petroleum was cooked long enough, with enough pressure, and run through the right catalyst, a higher quality anti-knock fuel would result. This trend in research did, in fact, result in the largest increase in anti-knock quality over the years.

Charles F. Kettering, on the other hand, was working on research problems for the automotive industry. His Dayton Metal Products Co. was merged with General Motors in 1919 and became the core of GM's research division.

Charles Kettering

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

Kettering’s fuel research had opened two very interesting doors. The 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 cellulosic biomass had the potential to compete with petroleum over the long run, they believed.

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.

Midgley, Boyd and others in the lab “danced a very unscientific jig” and hurried off to include Kettering in their victory party. Holding a test tube full of the stuff in his fingers, Kettering suggested, perhaps ironically, the name “ethyl” for the chemical compound tetraethyl lead. Although the term referred to the ethyl alcohol solvent used to dissolve the lead, and utterly confused the question of high percentage versus low percentage solutions, the name Ethyl stuck. Within a few years "Ethyl" became a component of high grade gasolines.

References

• [i] Large-scale production of benzene was questionable. Even if all the coal mined in the U.S. in 1920 were used to supply benzene, only about 900 million gallons, or one-fifth of the U.S. gasoline supply would be replaced, he said.