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EXAMPLE NO. 4: THE HISTORY OF LEADED GASOLINE

Forensic investigations are often a combination of both scientific techniques and historical background studies. One example that is often used is the background to leaded gasoline. Gasoline service stations can be found on many street corners and, in fact, there were many more service stations in the United States in the 1960s than there are today. This means that potential sources of contamination criss-cross the country and can be found in just about every neighbourhood.
Today, the United States uses more than 300 million gallons of gasoline per day. No other country comes close to this number. Between the 1920s and the late 1980s, this gasoline contained lead. Because many of these underground tanks had been in the ground for decades, the leakage of leaded gasoline was a common occurrence. We are still finding leaded gasoline in the ground today, almost 10 years after it was banned.

Tetraethyl lead (TEL) was first introduced as a gasoline additive in 1923. After many years of research, TEL was discovered by researchers at General Motors in Dayton, Ohio. Credit for its discovery is normally given to Thomas Midgley, Jr., who later went on to discovery chlorofluorocarbons (CFCs). However, the research work was headed by Charles F. Kettering, who was the discoverer of many automotive inventions, such as the electric starter.
In the late 1800s and the early part of the 20th Century, automobiles were run on many different types of fuel, such as steam, alcohol, diesel fuel and natural gas. Gasoline was also used, but it was limited by a drawback known as “knock”. As the motor engines became more powerful and the compression ratios increased, a knocking or pinging would occur in the cylinders. This was caused by detonation of the fuel. TEL was introduced as a way of reducing that knock and it allowed engines to be produced of greater power.