The underrated sulfur is essential for life

The underrated sulfur is essential for life

Andrew Szydlo (74) is not only a chemistry teacher at Highgate School in London, he also gives spectacular and acclaimed lectures at universities and at festivals, where he likes to “make things discolour, burn and explode”, as he explains on the phone. . And it just so happens that Szydlo has just published a 34-page essay on sulfur. He calls the element “seriously undervalued.” In his essay he describes sulfur as “the most remarkable substance ever.”

In high schools, Szydlo grumbles, sulfur is only dealt with by acid rain. That’s so negative. “Did you know that sulfur is essential for life on earth?” It is found in two of the 21 amino acids (methionine and cysteine) that make up proteins. And there are also bacteria that do not use oxygen but sulfur as a source of energy and metabolism. “Students learn about the carbon cycle and the water cycle, but why not the sulfur cycle?”

Rotten eggs and matches

For the general public, Szydlo continues while talking, sulfur mainly evokes associations “with rotten eggs and matches.” In other words: stench and flammability, the two properties to which sulfur owes its fame for thousands of years. It was once brimstone called, burning stone. Because the yellow deposits on rocks, often found near volcanoes, ignite easily. This concerns elemental sulphur, usually in the form of S8. “A stench can rise from the same volcanoes that you can also smell in swamps and sewers.” That’s H2S, hydrogen sulfide. It is produced by bacteria.

The combination of stench and fire, especially near volcanoes, means that sulfur used to be associated with “evil, demons, death, eternal damnation and hell,” Szydlo writes in his essay.

In it he also discusses the importance of sulfur for the alchemists in the Middle Ages. The right ratio of the yellow sulfur to the silvery mercury would produce the coveted gold. Inspiration for this idea, Szydlo writes, came in part from the mineral pyrite, which has “the superficial appearance” of gold but is a compound between iron and sulfur. So fake gold.

Huge mountains of sulfur

“Do you know what the most important source of sulfur is today,” Szydlo asks. “The fossil industry.” Fossil fuels contain small amounts of sulfur compounds. Until the 1970s, they were burned and ended up in the air. But when it became clear that they caused acid rain and tree death, regulations were introduced for the desulfurization of fossil fuels. Result: enormous mountains of sulphur. “These mountains are largely processed into sulfuric acid, one of the most important raw materials in the chemical industry.”

A day after the conversation, another forgotten question is emailed to Szydlo. Or he knew that scientists are investigating the extent to which the climate can be cooled by enormous amounts of sulfur dioxide (SO2) into the stratosphere? Just like volcanoes do. S.O2 can block sunlight. “No, I didn’t know that,” he writes. He immediately started reading more about it. “It seems to me a far-fetched idea, very difficult and expensive to implement.”

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