Harkins’ helix

Figure 315 is an updated Harkins helix published in 1934. The truly distinctive aspect of science is its ability to make predictions and test them—the... 

FIGURE 313. The 1916 Harkins-Hall periodic helix of the elements (from Journal of the American Chemical Society, 1916, with permission of The American Chemical Soci-ety). 

FIGURE 315. Later version of the Harkins-Hall periodic helix including the 1923 diS covery of halfnium (Hf, 72—not a rare earth as some originally thought) and the isok tion of rhenium (Re, 75) in 1925, although it is not explicitly named here. (Used with permission from Journal of Chemical Education, 1934.)... 

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