Boltwood, Bertram Borden

Boltwood/ Bertram Borden (1870-1927) American nuclear chemist who studied the radioactive breakdown of elements, and first discovered how to apply the ratios of lead to uranium in geological specimens in order to calculate their age. This, and other associated methods, was to bring new standards of accuracy into geology and paleontology. He discovered the radioactive element ionium. 

Bertram Borden Boltwood, 1870-1927. Professor of chemistry and physics at Yale University. Discoverer of the radioactive element ionium, the parent of radium. Ionium was discovered independently at about the same time by Hahn and by Marckwald. 

Editor s outlook. Bertram Borden Boltwood, . Chem. Educ., 6, 602-4... 

So constant and characteristic is the majestically slow decay of uranium that it can be used to measure the age of the earth. In 1907, the American chemist Bertram Borden Boltwood (1870-1927) suggested that the lead content of uranium minerals would serve as guide in this respect. If it is assumed that all the lead in the mineral originated from uranium decay, it would be easy to calculate how long a time must have elapsed to bring that amount of lead into existence. It was eventually calculated in this way that the solid crust of the earth must have been in existence for at least four billion years. 

These investigations uncovered the problem that some of the new elements were so similar to familiar elements that once mixed with them they could not be separated again. Thus in 1906 Bertram Borden Boltwood (1870-1927) of Yale University was unable to separate ionium (the immediate precursor of radium in the uranium series) from thorium. Similarly, Georgy Hevesy (1885-1966) was unsuccessful in his attempts to separate radium D from lead. 

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