Sulfur

Sulfur, with its unappealing rotten-egg smell, has been known to humankind for thousands of years. The element is mentioned in the Torah and in the Christian Bible (the term “brimstone” refers to sulfur). Sulfur has been known in China since at least the sixth century BCE, and the Romans mined sulfur on the island of Sicily. In the ancient world, sulfur was used in sulfur matches, in bleaching cloth, in making wine, and as a medicine, among other things.

The alchemist Jabir ibn Hayyan, also called Gerber, thought that all metals contained sulfur. He theorized that base metals like copper could be transmuted into gold by the right process. Although Gerber, and the alchemists who followed him, were wrong about this, their work did give rise to modern chemistry in the 17th, 18th, and 19th centuries!

In the 18th century, Antoine Lavoisier, who is considered one of the first modern chemists, suggested that sulfur might be an element. In 1809, French chemists Joseph Louis Gay-Lussac and Louis-Jacques Thénard proved this. The Frasch process, developed in the 1800s, made it possible to extract large amounts of sulfur from underground.

In recent decades, the discovery of large elemental sulfur deposits has become increasingly rare. That’s why today, most sulfur is produced as a byproduct of oil and other hydrocarbon production. But you still don’t want to smell it!

Sulfur is a non-metal that comes in several allotropes, or forms, that have different qualities. The most common allotrope, octasulfur, is lemon yellow and crystalline. Solid sulfur is odorless, brittle, and insoluble in water.

When melted, sulfur takes on a blood-red color. Spooky! Sulfur can also catenate, meaning that it can bind to itself in chains.

Sulfur has too many uses to count! Much of the world’s sulfur is used in sulfuric acid, which makes possible the production of products that range from fertilizers to explosives (including the gunpowder used in firearms and fireworks), fuels, paints, detergents, paper, rubber, concrete, and antifreeze.

In 1839, Charles Goodyear discovered that combining rubber and sulfur in the presence of heat would cause the rubber to vulcanize, meaning stiffen. This discovery led to the invention of the modern automobile tire (and, indirectly, to the creation of the Michelin Man).

Sulfur makes many compounds. In fact, it forms compounds with every element, except the noble gases. Sulfuric acid (H₂SO₄) is a highly corrosive substance that has many industrial applications. Organosulfur compounds, of carbon and sulfur, contribute to the bad smell given off by decaying plants and animals, but these compounds also come in many classes and have many applications.

Sulfur dioxide is an air pollutant produced by burning coal and heating oil and that can oxidize into sulfuric acid to be precipitated as acid rain. Other sulfur compounds, such as trifluoromethyl sulfur pentafluoride, play a key role in maintaining the Earth's climate. 

Scientists have characterized 24 sulfur isotopes. Four of these isotopes are stable, or non-radioactive. Ninety-five percent of naturally occurring sulfur is sulfur-32. Sulfur-35 is the only sulfur isotope with a half-life of more than three hours (its half-life is around 87 days). This isotope is formed when cosmic rays strike atmospheric argon molecules.

By mass, sulfur is the fifth most common element on Earth. Historically, sulfur was found around volcanoes and hot springs. It’s found throughout nature in a range of minerals, including iron pyrite (aka fools’ gold), gypsum, galena, barite, and others.

In the late 1800s, German-born American chemist Herman Frasch developed the Frasch process to extract sulfur from underground formations. By heating sulfur deposits with steam, the sulfur would melt and could be pumped to the surface.

Today, most sulfur is produced as a byproduct from refining hydrocarbons, including petroleum and natural gas. China, the United States, and Canada are the world’s top sulfur producers.