100 YEARS AGO

The Paris correspondent of the Chemist and Druggist states that science is represented at the Salon by several portraits of average merit. The best is that of Dr. Vaillard, head army surgeon and professor at the Val de Grace Military Hospital, where he is known to two or three generations of army pharmacists who have followed his lectures. Dr. Vaillard is of middle age, and is shown standing, in regimental dress, with the Cross of the Legion of Honour on his tunic. His left hand is leaning on a laboratory-bench, on which are a microscope and a variety of analytical appliances… One would like to see more of this class of picture, but must suppose artists find no market for them.

From Nature 10 May 1900.

50 YEARS AGO

In 1940 the first isotopes of the elements 93 (neptunium) and 94 (plutonium) were produced, and four years later the artificial creation of the elements 95 and 96 (americium and curium) was accomplished … Now from the Radiation Laboratory of the University of California comes the news that within the past few months the next two transuranic elements have been made and identified. The first announcement, released early in January of this year, concerned element 97. S. G. Thompson, A. Ghiorso and G. T. Seaborg, aided by a number of other physicists and chemists working under the auspices of the U.S. Atomic Energy Commission, had bombarded the isotope of element 95 (americium), of atomic weight 241, with 35-MeV. helium ions accelerated in the California 60-in. cyclotron and thereby obtained a nuclide with a half-life of 4.6 hr. and probable atomic weight 243. It decays by electron capture, with approximately 0.1 per cent α-branching; there seem to be three α-particle groups, that of 6.72 MeV. having the highest energy. The production of element 98, which has just been reported by the same three authors and K. Street, jun., was achieved in an analogous way. By irradiating the isotope of element 96 (curium) of atomic weight 242, in the same cyclotron with helium ions of the same energy, a new nuclide was formed which decays with a half-life of about 45 min., emitting α-particles of energy 7.1 MeV. The possible and, for theoretical reasons, likely decay by electron capture has not yet been observed. The atomic weight should be 244.

From Nature 13 May 1950.