Titanium can't solve every problem we face in manufacturing, but it has a high-caliber strength-to-weight ratio, is incredibly light and resists even the most brutal corrosives. It's also not that hard to mine, as the ninth most abundant element on Earth and the fourth one most commonly used in construction. We've even found it in rocks on the moon. Without metallurgist William Kroll, we wouldn't have access to the refined titanium used so prevalently. His Kroll Process is still used today to purify this unique metal, almost 75 years after he originally developed it.
While the Earth's crust is heavy with titanium, the element doesn't just appear by itself in nature. Before you can use it, you have to separate the ore from other minerals that are bonded to it. In this form it was first discovered in 1791 by William Gregor, who was both a clergyman and a geoscientist. It got its name though from Austrian chemist Martin Klaproth, who first called it "the reddish brown calx" and then decided that wasn't descriptive enough and dubbed after the Titans of Greek myth. We're talking about gods who commit deicide, dismember babies, boil limbs and are then get disgorged by their own children. Klaproth wasn't messing around when he named this metal after those immortals of doom.
It was over a hundred years after titanium was discovered that someone figured out how to isolate it. American chemist Matthew Hunter tried first in 1920, but his process used sodium and was unable to produce quantities worth the investment. Then in 1937, Luxembourg's William Justin Kroll took Hunter's technique and used magnesium instead of sodium. When World War II began, he fled to the United States and continued his work with the Union Carbide Company and the U.S. Bureau of Mines. He refined his process by 1940 so titanium could finally be produced on a commercial scale. While Kroll's process is complicated and still requires up front expenditures, no one else has yet to develop a better way to replace it.
Here's how the core of how Kroll's process works:
- By combining the titanium dioxide in the raw ore with chlorine, a light yellow liquid called titanium tetrachloride is produced.
- This liquid is then mixed with molten magnesium, stripping away the chlorine atoms and leaving behind pure titanium in a "sponge" form. This has to be done in a contained atmosphere of argon gas because air reacts poorly with the sponge and will spoil the final product.
- The sponge is then compressed to squeeze the leftover magnesium chloride out.
- By using acids and distillation, the sponge is then purified, melted into sludge and formed into ingots.
- These titanium ingots are then converted into standard shapes like bars, plates and tubes. Later they can be fabricated into other forms to meet our final manufacturing needs.
Thanks to William Kroll's work, titanium is now used to contain nuclear waste and protect the crafts we launch into space. No wonder Klaproth named it after powerful ancient gods.
Lots More Information
- Reynolds, V. "Researchers find way to slash titanium production costs." American Metal Market. Volume 109. No. 29. Page 14. 2001.
- Lazarus, P. "Titanium." Professional Boatbuilder. Vol. 132. Pages 62 - 72. 2011.
- Schumerth, D.J. "Titanium enjoys 30 years of successful service." Power. Volume 148. No. 3. Page 63. 2004.
- Schumerth, D.J. "Titanium tubing Still Going Strong After 40 Years." Power. Volume 155. No. 7. Pages 58-60. 2011.
- Woodford, C. "Titanium." Marshall Cavendish. 2003.
- Encyclopedia Britannica. "William Justin Kroll (German chemist)." (Accessed online January 15, 2014.) http://www.britannica.com/EBchecked/topic/323749/William-Justin-Kroll