Tetraethyl Lead (You think your Excursion’s changing the environment? Think bigger. Much bigger. Part 1 of 2)
15th May 2006
Tetraethyllead is another one of those organometallic compounds that is absolutely bizzare unless you work with them yourselves. It’s got lead in it - in fact, it’s over 60% lead by weight, but it’s a clear, lipophilic liquid. It has the effect of decreasing the tendency for gas to combust prematurely in an engine, or “knock.” That is, when added to gasoline, it increases its octane rating. This is all an octane rating is - a measure of a fuel’s propensity to prevent knock. 87 is more likely to knock in a high-compression engine than 91.
Here is the structure of tetraethyl lead:
Combustion of TEL released various lead compounds, which was bad enough. Some of the lead came out as lead metal, which actually would deposit on your engine (great, especially since engine manufacturing precision wasn’t so hot until the Japanese took us to school in the 70’s). Too much lead accumulating was a problem, though; this would kill your engine quickly. We went with an equally troublesome solution: the use of ethylene dibromide as a lead scavenger:
This caused much of the lead to come out of the exhaust pipe as lead bromides, which are volatile (evaporate)! This meant that every car was pumping out gaseous lead. Inhaling something is pretty much the quickest way to get something in your blood short of injecting it, so this made everyone take in lots of lead.
Since tetraethyllead was banned, human lead levels have dropped precipitously . It is hard to overstate how much this compound contributed to everyone’s lead burden while it existed.
TEL was invented by Thomas Midgley, whom J.R. McNeil later described as having the dubious honor of “[having] had more impact on the atmosphere than any other single organism in earth history.”
Midgley had a rough time of it. In public, he insisted TEL was completely safe, going so far as to immerse his hands in it and breathe the fumes deeply. At one point, however, he had to take a (secret) vacation to recover from lead poisoning. You can’t keep a good man down, though. He has one more problem child, which we’ll talk about tomorrow.