Elements Old and New

Abstract

THE historical development of the conceptions of ‘atom’ and ‘element’ were outlined by Prof. James Kendall, professor of chemistry in the University of Edinburgh, in delivering the twenty-fifth Bedson lecture in Newcastle-upon-Tyne on March 2. He pointed out that there have been four great periods of chemical discovery, corresponding quaintly with the four ‘elements’ of the Greeks, fire, air, earth, and water. The first was the phlogistic period, ending with Lavoisier; the second, the great period of research on gases; the third, the gradual rounding off of the chemistry of the rare earths; and the last opened up by the discovery of heavy water. It was mentioned that there should be nine kinds of water, and more than a hundred varieties of ethyl alcohol “some perhaps more exhilarating”. Of great interest was the account of a research just concluded in the (Edinburgh laboratories in which calcium from a § mineral rich in potassium has been shown to have a slightly higher atomic weight owing to the isotope derived from the radioactive isotope of potassium, K⁴¹. This has been confirmed by Allison in the United States, using his magnetoroptic method. Two pegmatites of very different ages, but of which the younger contains much less calcium than the older, have indicated a half life period of 9×10¹¹ years for potassium in, agreement with one of two measure ments by direct physical methods. The lecture was enlivened by numerous amusing reminiscences and suggestions, especially concerning the new element D (or, according to Prof. H. E. Armstrong, Ww !).