We continue to review some of the most important materials in heat treatment and metallurgy.

Sulfur (chemical symbol: S)

Sulfur is a dull-yellow, lustrous, odorless and brittle material that reacts with all elements, except for gold, platinum, iridium, tellurium and the noble gases. In nature, sulfur is often found in sulfide and sulfate mineral deposits and can also exist in its raw elemental form. Sulfur had many uses in ancient times and was mentioned in early texts in ancient India, ancient Greece, China and Egypt. In the Bible, sulfur is called brimstone. When burned, sulfur produces a deep-blue color.

Sulfur became acknowledged as a chemical element (rather than a compound) in 1789 when Antoine Lavoisier included it in his famous list of the elements. Lavoisier, a brilliant chemist and scientist, also recognized and named the elements oxygen (1778) and hydrogen (1783). Considered by many the “father of modern chemistry,” he also contributed to the development of the metric system and established the principle of conservation of mass in chemical reactions. Although there is no clear documentation, it is speculated that sulfur may have gotten its name from the Arabic word “sufra,” meaning yellow.

A nonmetal, sulfur is the 10th-most-common element in the universe. Sulfur’s largest use is in the production of sulfuric acid, which is a component of fertilizers, batteries and cleaners. Sulfur is also used to refine oil and in processing ores. Pure sulfur has no odor; the rotten-egg odor that it is known for only occurs when combined with other elements (i.e., sulfur dioxide. Sulfur compounds called mercaptans, for example, give skunks their offensive odor. Rotten eggs and stink bombs get their distinguishing aroma from hydrogen sulfide (H2S).

Sulfur is used to make gunpowder (aka black powder), the precursor to today’s smokeless powder, which was the earliest-known explosive. Its recipe was found in a Chinese text dated from the year 808 AD. Sulfur is thought to be one of the constituents of “Greek Fire,” (Fig. 2) a terrifying weapon akin to a flamethrower used during naval battles by the Byzantine Empire. 

Gunpowder consists of sulfur, charcoal and potassium nitrate (saltpeter, KNO3). The sulfur and charcoal provide the fuel, and the saltpeter is an oxidizer. Other common uses for sulfur include: household matches, fireworks, fungicides, insecticides, fumigants and in the vulcanization process of rubber. Sulfur is also important for the manufacture of phosphate fertilizers and in the treatment of certain skin diseases. Since sulfur generates poisonous sulfur-dioxide gas when ignited, burning sulfur has been used for centuries as a fumigant.

Here are some interesting facts about sulfur.

  • Atomic number: 16
  • Atomic weight: 32.066
  • Melting point: 388.36 K (115.21°C or 239.38°F)
  • Boiling point: 717.75 K (444.60°C or 832.28°F)
  • Density: 2.067 grams per cubic centimeter
  • Phase at room temperature: Solid
  • Element classification: Non-metal
  • Period number: 3   
  • Group number: 16   
  • Group name: Chalcogen



  1. KnowledgeDoor (www.knowledgedoor.com)
  2. Jefferson Lab (https://education.jlab.org/)
  3. Geology.com (https://geology.com/)
  4. ATI (http://allthatsinteresting.com/)