The Flash of Genius, 5 Collected by Alfred 6. GarreH
Ohio State University Columbus
Lead Tetraethyl: Thomas Midgley, Jr., T. A. Boyd, and C. A. Hochwalt
In 1919 the engineers in the automobile industry were concerned about the engine-knocking produced by the gasoline used a t that time. Previous to that time iodine was known to be an anti-knock agent. Three young engineers, Thomas Midgley, T . A. Boyd, and C. H. Hochwalt, were given a problem by Charles Kettering (the research director of their company, The General Motors Company), of finding something which could be added to gasoline to prevent it from knocking. They set up a test engine in their laboratory and proceeded to test each material they could find that was soluble in gasoline. After many teats by trial and error, they found several compounds that would prevent knocking. One of the best of these was the compound of selenium called selenium oxychloride. Following this one was diethyl tellurium which nras found to he several times better than any discovered up to that time. Now their work shifted from a trial and error procedure to planned research. They and their fellow worken planned a. systematic study of the anti-knack properties of campounds of elements on the basis of the poeition of the elements in the periodic table; and they concentrated their attention on the elements near to eelenium and tellurium. After many tests they found that an organic compound of lead, called lead tetraethyl, was an excellent anti-knack agent far gruoline; their discovery led to the ethyl gasoline used all over the world today. The early part of this research was by trial and error and the latter part m e carefully planned. I n his Perkin Medal address,l,s Midgley summarized the search as follows:
"In the search for a material with which to control knocking in an internal combustion engine, the following determinations were arrived a t by the Edisonian method: "1. Elemental iodine, dissolved in motor fuel in very small quantities, greatly enhanced the anti-knock characteristics of the fuel (the basic discovery). "2. Oil-soluble iodine compounds had a similar. though modified effect. "3. Aniline, its homologs, and some other nitrogenous compounds were effective, though their effectiveness varied over a wide range depending upon the hydrocarbon radicals attached to the nitrogen. "4. Bromine, carbon tetrachloride, nitric acid, hydrochloric acid, nitrites, and nitro compounds in general increased knocking when added to the fuel and air mixture. "5. Selenium oxychloride was extremely effective as an anti-knock material.
'
MIDGLEY,THOMAS,JR., Ind. and Eng. Chem., 29, 2 4 1 4 (1937) (the Perkin Medal address). Personal correspondence. J B o ~ T. ~ ,A,, S.A.E. Quarterly Transaction, Vol. 4, No. 2, April 1950. 'BOYD,T. A,, "The Profeeeional Amateur, the Biography of Charles FranklinKettering," E. P. Duttonand Co., Inc., 1957. 6 K ~ D. H., ~ "The ~ Genius ~ of ~ Industrial ~ ~ Research," ~ , Reinhold Publishing Co., New York, 1948, pp. 43-47.
414
/
Journal o f Chemical Education
"6. A large number of compounds of other elements had shown no effect. "With these facts before us, we profitably abandoned the Edisonian method in favor of a correlation procedure based on the periodic table. What had seemed a t times a hopeless quest, covering many years and costing a considerable amount of money, rapidly turned into a 'fox hunt.' Predictions began fulfilling themselves instead of fizzling. Diethyl selenide was prepared and worked as expected; diethyl telluride next fulfilled our predictions, and seemingly our wildest dreams of success had been realized. There are, however, good reasons for not using tellurium compounds. A systematic survey was then conducted using a periodic arrangement suggested by R. E. Wilson. The ethyl and phenyl derivatives of the elements on the right of the arrangement according to vacant places were prepared and their effects measured in motor operation. The results were plotted as anti-knock effect us atomic number. Tin was the first element investigated from the group immediately to the left of those previously reported. Its ethyl derivative was studied. This compound exhibited a much more powerful effectthan had been expected. We thereupon predicted that tetraethyl lead would solve the problem. The record of the past decade has borne out that prediction." Midgley continues, "The assistance of T. A. Boyd and Carroll A. Hochwalt in the development work which led to the discovery of the utility of tetraethyl lead in motor fuels cannot be overemphasized." Boyd's eummmyP-'is as follows:
"I. It was in early 1919 t,hat the search for a practical anti-knock agent began in a formal way. (But shortly before World War I the anti-knock effect of iodine had been discovered.) "2. I n the early work we tested both materials that we could find and those few we could make with our limited facilities, "3. While 'trial-and-error' may properly be used perhaps in respect to the method of the early research, the search was systematic even then in that the initial plan was ultimately to test a compound of each one of the known elements. At that time we did not know, however, that it had to be the right compound. "4. Tetraethyl lead came to be used not only in 'Ethyl' gasoline but also in practically all gasoline, including airplane, which is still so today. a. Further with regard to what is called the 'trialand-error' method of research, I may quote a- saying
".
of Charles F. Kettering, who thinks that method of prospecting has an important place in fields where knowledge is limited. And in his view this includes
more fields than is commonly supposed. 'Why don't they call it the trial-and-success method? That is what it really is,' he has said."
Volume 39, Number 8, August 1962
/
415
