Sulfur is an important precursor to many industrial processes. Much of it goes into making sulfuric acid, a common reactant and a component of fertilizer. In the nineteenth century, Sicily dominated the production of this element. Deposits were found in the United States, too—notably in Louisiana and Texas—but they were much deeper and more difficult to mine. It may not have been gold, but unlocking this yellow substance could be a deeply profitable business.
One man had the answer, and from it derived the process that now bears his name. German-born Herman Frasch (1851-1914) settled in the United States and made a name for himself removing unwanted sulfur from petroleum. In the 1890s sulfur itself became the focus of his attention, and he sought a way to mine the deep-set mineral.
His solution was to bore a drill hole down to the layer containing sulfur. An arrangement of three concentric pipes is fed into the hole. Superheated water at 338°F (170°C) is pumped through the central pipe, down to the rock layer. Sulfur melts at around 239T (115°C), so it becomes liquid when in contact with the superheated water. Forcing compressed air down another tube causes the molten sulfur to ascend as a slurry to the surface, where it solidifies into a highly pure form readily usable by industry.
Although Frasch was unable to make a sustainable sulfur-mining business for himself, the process he developed eventually enabled the United States to become self-sufficient for sulfur production, fueling a boom in its chemical industry sector. The Frasch process remained the world's dominant form of sulfur production until the 1970s, when the element was more economically obtained as a by-product of natural-gas and oil refining.
