# Why would tellurium + sodium hydroxide have worked as a good anti-knock gasoline additive (if it wasn't so smelly)?

The April 22, 2022 Veritasium video The Man Who Accidentally Killed The Most People In History mentions several aspects of the historical use of tetra-ethyl lead in gasoline, the resulting widespread distribution of lead in the environment and within people, and the consequences of that.

As part of the story, it mentions that during Thomas Midgley Jr.'s search1 for a gasoline additive that would reduce premature detonation in a high-compression gasoline engine, a tellurium-based additive was tried. The graphic in the video indicates "tellurium + sodium hydroxide".

Kettering wanted to find an additive which would increase the octane rating of ordinary fuel and eliminate knocking in high-compression engines. So he hired 27-year-old engineer Thomas Midgley Jr. Midgley experimented with all sorts of compounds, from melted butter and camphor, to ethyl acetate and aluminum chloride. He later wrote "Most of them had no more effect than spitting in The Great Lakes."

Ethanol was an interesting exception, it did stop the knocking, but you needed a lot of it, about 10% of the fuel mixture to be effective. That much ethanol would be expensive and hard to turn a profit on. And Midgley was really after an additive that was cheap, easy to produce and effective even at low concentrations. So he kept trying.

Then he hit on tellurium. It worked wonderfully as an anti-knocking agent, but it had a terrible smell. You couldn't get rid of it by changing clothes or bathing. His wide was so offended by the stench that he had to sleep in the basement for seven months. Midgley wrote: "I don't think that, although this doubled fuel economy, humanity would suffer this smell."

Question: Why would tellurium + sodium hydroxide have worked as a good anti-knock gasoline additive (if it wasn't so smelly)?

According to the second quote from Midgley, in addition to reducing/stopping engine knocking it also improved mileage substantially. By what mechanism is a tellurium-based additive able to do this?

1at the behest of Charles Kettering after the higher compression engine of the Model 30 Cadillac exhibited problems with knocking (premature detonation of fuel-air mixture before the electrical spark was triggered)

The only reference to sodium hydroxide in the video is this visual cue in the animation:

Additional supporting screenshots:1, 2

• Please separate these out. You have several questions in your post. Apr 28, 2022 at 0:31
• Not an answer, but I am glad Te never got used as an anti-knock ingredient! Besides Te being rather rare, its compounds are notoriously nasty smelling: hydrogen telluride supposedly smells like rotten horseradish. Worse still, exposure results in the human body slowly, over months, eliminating the tellurium compounds in the breath and sweat. We lucked out on this one!
– Ed V
Apr 28, 2022 at 2:20
• See/listen also Episodictable.com: 52. Tellurium: To Hell You Ride Apr 28, 2022 at 6:20
• Tellurium was an effective additive which Midgley knew because he tested engine performance with it as an additive. It probably works in ways similar to lead additives. but the side-effect of small was unacceptable. Apr 28, 2022 at 10:34
• See this for the actual mechanism: Callear, A. B., and R. G. W. Norrish. “The Behaviour of Additives in Explosions and the Mechanism of Antiknock. I.” Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences, vol. 259, no. 1298, 1960, pp. 304–24, jstor.org/stable/2413734. Accessed 28 Apr. 2022. Apr 28, 2022 at 19:13

## 1 Answer

Midgley tried various compounds, especially $$\ce{(C2H5)2Se}$$, $$\ce{(C2H5)2Te}$$, $$\ce{(C2H5)4Sn}$$, and $$\ce{(C2H5)4Pb}$$, which all work as anti-knock agents with similar mechanisms.

The oldest method for the synthesis of dialkyl tellurium is the reaction of disodium telluride with alkyl halides. The required solution of disodium telluride can be prepared from tellurium and a reducing agent in aqueous sodium hydroxide.

So I guess they simply put a part of the first step (tellurium and sodium hydroxide) on the label for the video.

Midgley, T.; Boyd, T. A. The Chemical Control of Gaseous Detonation with Particular Reference to the Internal-Combustion Engine. J. Ind. Eng. Chem. 1922, 14 (10), 894–898.

• See this for the actual mechanism: Callear, A. B., and R. G. W. Norrish. “The Behaviour of Additives in Explosions and the Mechanism of Antiknock. I.” Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences, vol. 259, no. 1298, 1960, pp. 304–24, jstor.org/stable/2413734. Accessed 28 Apr. 2022. Apr 28, 2022 at 19:10