From the mid 1920's until the mid 1980's motor gasoline fuel contained an additive, tetraethyllead, that improved fuel performance by preventing preignition in the cylinders of the engine. Preignition resulted in damaging and efficiency and power reducing knocking. Tetraethyllead is a toxic liquid that killed more than 40 chemical workers during its early development and manufacturing. Nevertheless, motor companies, oil companies and the US government authorized the manufacture, distribution and use of tetraethyllead (TEL) in gasoline throughout the world.
The Chemistry: Automotive fuels derived from petroleum propel our cars by converting the energy of combustion to heat and work. The challenge for an efficient, powerful engine is to maximize the work available. The second law of thermodynamics teaches this can be done by designing engines with high compression ratios. However, problems of uneven fuel combustion and knocking must be overcome through fuel reformulation or by finding an appropriate additive.
The Questions: How did lead compounds, whose extreme toxicity were known for more than a century before they were introduced into gasoline, become an accepted and everyday component of the fuels we use - and of the air we breathe and the ground upon which we walk? Students will go through a series of units outlined below and end with a case discussion on how automakers, oil companies and the government might have better dealt with the issues of gasoline quality in the early 20th century.
- 4: Tetraethyllead - Toxicity
- Throughout 1922, as the first plans were made to develop tetraethyl lead, Midgley had received an alarming letter from Charles Kraus of Pottsdam in Germany. Kraus had worked on tetraethyl lead for many years and called it "a creeping and malicious poison" that had killed a senior scientist at his university.
- 10: Removal of Lead
- In chemistry we relate macroscopic, observable change to transformations at the molecular level that go unseen through the shorthand of symbolic representation. For the most part, we are comforted by the fact that we can at least observe the macroscopic. Here is a wonderful representation of the way chemical reactions take place that may help you understand chemical kinetics and thermodynamics.