Sulfur — Frequently Asked Questions

Because almost all of it is recovered rather than mined for its own sake. Sulphur compounds must be stripped from natural gas and crude oil to meet fuel and emissions legislation, and the Claus process converts them to elemental sulphur. Output therefore tracks oil and gas throughput rather than sulphur demand, which makes the price unusually volatile.

Sulphuric acid, which accounts for around 85 percent of consumption. Sulphuric acid is the highest-tonnage manufactured chemical in the world, and most of it goes into phosphate fertiliser production, where it digests phosphate rock. The remaining sulphur serves rubber vulcanisation, agriculture, mining chemistry and bitumen modification.

It forms sulphide bridges between polymer chains, crosslinking a soft plastic mass into an elastic solid that recovers its shape. The number and length of those bridges determines the properties: fewer crosslinks give a soft flexible rubber, more give a harder one. The process needs accelerators and activators such as zinc oxide to run at commercial speed.

Because particle size governs efficacy. Sulphur works by contact and by sublimation, and finely micronised particles give far more surface area, better leaf coverage and more effective vapour action than coarse material. It is one of the oldest fungicides still in use and remains permitted in organic production, where it controls powdery mildew and mites.