Dr. Thomas Midgley: "From the Periodic Table to Prod~ction"~ Mlriam C. Nagel Avo" High Schwi Avon. CT 06001 "Happily neither Tom nor I was a n orthodox chemist or thermal engineer, so we were wholesomely ignorant of the obstacle^."^ Charles F. Kettering was describing Thomas Midgley, Jr. and himself when Dr. Midgley joined Kettering's Dayton Engineering Laboratory in 1916 and accepted the challenge of finding a way to reduce knock in internal combustion engines. The problem was poorly understood. Some blamed knock on the battery ignition system (part of the self-starter) or on carbon deposits, others thought it was related to fuel volatility. The first thing Midgley, a 1911 Cornell graduate with a degree in mechanical engineering, had to do was learn more about engine knock. To do this, he developed an optical device with a bouncing pin la trace I he p r e s s ~ mchanges in nn engine. This invmtion, later called the MidgI6.y indicator, allowed hint to measure knock quantitatively. Knock was eventuallv discovered to be the result of fuels detonating instead of burning smoothly. It grew worse as the compression ratio of an engine increased. Early experiments showed that kbocking decreased if the easoline was colored red. Midelev followed this lead and tried adding iodine to the fnel. ~ & l h s t i o n did improve, and he theorized that the color absorbed radiant heat. increasine fuel volatility. He related the phenomenon to red-backed &ing arbutus which blooms under the snow. The theory was short-lived for colorless ethyl iodide proved to be even better a t reducing knock! Dr. Midgley decided that the element iodine was responsible for the improvement because of its atomic structure. Though he wadencouraged by some success in finding a chemical additive to reduce knock, he felt a need to know more chemistry and intently studied the subject. Years later he accurately described himself as a research chemist. He received four major awards for his contributions to chemistry: the Nichols medal in 1923, the Perkin medal in 1937, the Priestly medal in 1941, and the Willard Gibbs medal in 1942. He received a Doctorate in Science from the College of Wooster in 1936. In his search for the best antiknock additive, Midgley tried more than 33.000 different comuonnds. He called this anproach the ~ d i s o n i a nmethod. ~ l & gthe way he found seveial nitroeen comvounds. includine aniline, which were effective. but they producrd ohnoxiuus bdors. He finally decided to use the veriodic table roordin:~khis findincs and concencratd his efforts on compounds near those with antiknock properTitle taken from Midgley. T. and Boyd. T. A.. J. Ind. & Eng. Chem.. 29. 741 119371 --.-..\.--.,.
Hew. Ernest V., "Fire of Genius," Anchoi WesslDoubleday,Garden City. N.Y.. 1978, p. 287. New York Times, January 9, 1937. D. 19. col. 8. 'Johnston. D. O., et al., "~hemistryind the Environment,'. W. 8. Saunders. Philadelphia. 1973, p. 398. 496
Journal of Chemical Education
ties. He used the quantitative data he collected and related it to the positions of elements on the table to develop trends. On December 9, 1921, almost six years after he began his search, Midgley discovered the outstanding properties of tetraethyl lead. When Dr. Midelev - .received the Perkin medal his achievement was commended, "Midgley's work resulted in the creation of the entire ethyl gasoline industry with all that it implies-use of higher compression engines, greater flexibility of automobile operation and other advances. Tetraethyl lead in motor fuels adds fifty times as much horsepower annually to American civilization as that which will he supplied bv .. Boulder Dam."3 While tetraethyl lead did improve engine efficiency, deposition of lead on the valves was aprohlem. It was solved by the addition of small amounts of ethylene dihromide. The bromide and lead combine to form lead bromide which is released in the exhaust as a particulate. Leaded gasoline contains 2 3 mL of a mixture eenerallv about 62% tetraethvl lead. 18%ethylene dibromide, l"8% ethilene dichloride and ;%dye and other suhstances. This mixture puts 2-4 g of lead in a gallon of gasoline.' A limit of 0.5 grams of lead per gallon, effective October 1980, has been set by EPA. The toxicity of lead has long been recognized. In 1922 before tetraethyl lead additives were approved, the U S . surgeon general appointed a committee to investigate the hazards of their use. The benefits of increased enaine and the fnel - vower . savings attainable with tetraethyl lead were enough to override their concerns. Ethyl gasoline went on sale February 2,1923. The ultimate dimensions of the impact of lead on the environment from the emissions of vast numbers of automobiles could not then he anticipated. Fuels with high octane ratings have less tendency to knock. Octane rating is determined by comparing, with a Midgley indicator and a standard engine, the knock of a particular fuel ~
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Readers of profile^ in ChemiJtly" who have an interest in t b histay of chemishV are encouraaed to submh manuscriots for oubiication in th 5 S e r m Authors sho~ld contact tne Fedwe Eaftor~ m r preparnng m a man.sCr pl 10 e n s l e lnot 1ne r SqeCl ha5 not )et noon assagneo Tns Feature €6 lor s a m reemg persons m o w eageaole n tne histmy 01 chemisby m review submitted manuscripts. imerested a m and pnentiii r e v i m may write to Roger R. Festa, Feahlre E d i i . 111 Winfieid Street. East Norwaik, CT 06855.
Roger R. Feda received his BA from St. Michael's College in 1972. his MAT from the University of Vermont in 1979. and is presently working on his GAS at Fairfield University. Mr. Festa has taught both high school chemistry and biology. He is currently on the facultyof Brim McMahon High Schmi rn Norwalk, Connecticut. He is an active member of the ACS. New York Academy of Sciences, American institute of Chemists, and Amer call A.;suc..~lor for me Aovancemenl 01 Sclence. he asma m n ol Itme hign Sihuol Cnem stry Commmee ol me WEslerII Connecticut Sccl on rca-ctmrman ot its Ea~caton Comm nee. an" a memoer of its Executive Board. He has published essays on science, history, and education in Chemunily, The Fairfield Chemest, and The Norwalk Hour. and h e has reviewed curricular materials for Science Books and F,lms.
to a mixture of 2,2,3-trimethylpentane, "isooctane," having a rating of 100 and normal heptane with a rating of 0. The percent of isooctane in the mixture that will experimentally give identical knock is the octane rating. Mixtures of hranched chains and aromatics, both less prone to knock, are used in no-lead fuels. The rapid growth of the ethyl gasoline industry taxed the production capacity of bromine in the United States. T o improve production, Dr. Midgley developed the commercial process to extract bromine from seawater. Although the largest use of hromine has been for the manufacture of ethylene dihromide for ethyl gasoline, other uses are being developed to replace that market. Dr. Midgley suggested in 1934 that gold might also some day be extracted commercially from seawater. Midgley was not only involved with the Ethyl Gasoline Corporation, of which he was first general manager and later vice president, but also he was general manager of General Motors Chemical Company which made refrigerators and air conditioners. The cooling agents then in common useammonia, methyl chloride and sulfur dioxide--were toxic and irritating. Dr. Midgley was asked to search for a nontoxic, nonflammable refrigerant. He started with a study of the periodic table for stable compounds with suitable boiling points. In spite of the toxicity of fluorine, he decided to try carbon tetrafluoride. T o prepare the CF4 he obtained five 1-02 bottles of SbFs from a laboratory supply house. He used one bottle to prepare a sample of the
gas for a test of its toxicity. The CFd proved perfectly safe to a lahoratory guinea pig. Midgley was encouraged and started looking for analogs of CF,. Luckily, he had selected the only pure sample of ShF3 for his first test. The second hatch of CFa killed the guinea pig. The remaining bottles of ShFs were all contaminated, producing highly toxic phosgene along with CFI. Midgley took only three days to develop a nontoxic, nonflammable refrigerant which he labeled Freon-12, dichlorodifluoromethane. There are now four freons, chlorofluorocarbons, in common use. The controversy over the use of freons as aerosol solvent propellants came after his death, by which time he had been granted over a hundred patents. In 1940, Dr. Midgley contracted polio which left him paralyzed. Undaunted by his handicap, he developed a harness to help him get out of bed. Unfortunately, he became entangled in the harness on November 2, 1944, and strangled. He was 55. Ironically, only a few months before his fatal accident, the theme of his presidential address to the American Chemical Society was that scientists beyond the age of 40 have lost the creativity needed for discovery and invention. "For genius and display take youth; for cold calculations and planned execution take age."5
New
York Times. September 11. 1944, p. 19, col. 6
Volume 58 Number 6 June 1981
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