Boltwood, Bertram Borden (1870–1927)
![Bertram Borden Boltwood](../../images/Boltwood.jpg)
Bertram Boltwood was an American chemist and physician who did important research in radioactivity which led to the development of the theory of isotopes. Boltwood discovered (1907) ionium – a radioactive isotope of thorium. He was professor of radiochemistry at Yale University (1910–1927).