The Betterton-Kroll process is an industrial process for removing bismuth from lead. The process was developed by William Justin Kroll and patented in 1922. Further improvements were developed by Jesse Oatman Betterton in the 1930s.
Calcium and magnesium are added to a molten lead-bismuth bath. The resulting bismuth compounds have higher melting points and lower densities than the lead, and can be removed as dross. The compounds are treated with chlorine to free up the bismuth. Temperature used in the process is about 380-500 °C(572-932°F) . The other major processes for separating the two metals are by fractional crystallization and by the Betts electrolytic process.
See also 
- de 410533, William Kroll, "Verfahren zum Ausscheiden einzelner Metalle aus Metallgemischen", published 1925-03-09
- de 615566, M. Lissauer & Cie in Köln a. Rh., "Verfahren zum Entwismutieren von Blei", published 1935-07-08
- zum Entwismutieren von Blei mit Erdalkalimetallen de 622135Verfahren zum Entwismutieren von Blei mit Erdalkalimetallen, M. Lissauer & Cie in Köln a. Rh., published 1935-11-21
- us 1428041, William Kroll, "Process for the separation and recovery of metals from metal alloys", published 1925-03-09
- Kroll, W.J. (1955). "How commercial titanium and zirconium were born". Journal of the Franklin Institute 260 (3): 169. doi:10.1016/0016-0032(55)90727-4.
- us 2205387, Betterton, Jesse O.; Lebedeff Yuril E., "Recovery of bismuth", published 1940-06-25
- us 2101975, Betterton, Jesse O.; Lebedeff Yuril E., "Refining lead", published 1937-12-14
- Samans, Carl H. Engineering Metals and their Alloys, 1949 MacMillan
- Ojebuoboh, Funsho K. (1992). "Bismuth—Production, properties, and applications". JOM 44 (4): 46–49. Bibcode:1992JOM....44d..46O. doi:10.1007/BF03222821.
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