The arc spectrum of palladium, its Zeeman effect and spectral type

Abstract

Palladium is a metal occurring in the eighth group of the periodic table of the elements. Of atomic number 46 and atomic weight 106·7, it is a member of the so-called triad—ruthenium, rhodium, palladium. In the vertical column of the table, palladium occupies a position between nickel and platinum. According to the alternation law governing the multiplicities of terms in the line-spectra of the elements, only odd multiplicities are to be expected in the even groups of the table, and vice versa . The numerous spectral regularities which have been discovered in the arc spectrum of iron, belong entirely to triplet, quintet, and septet systems. The arc spectrum of cobalt, on the other hand, has been shown by Walters to contain quartets. This would seem to indicate that the present grouping of these elements is erroneous, and that a division should occur between iron and cobalt, and probably also between cobalt and nickel. The behaviour of elements in the other groups of the table makes it probable that ruthenium and osmium, in the same vertical column, should be in the same group with iron, and that their spectra should be similar and should contain only odd multiplicities. Similarly, rhodium and iridium would be grouped with cobalt, and only terms of even multiplicity should appear in their spectra. The next group would then be nickel, palladium, and platinum, and again odd multiplicities would be expected. An analysis of the spectrum of nickel has been undertaken at the laboratory of the Bureau of Standards in Washington. Some photographs of the Zeeman effect of nickel have been made by the present writer, and the patterns observed indicate that the spectrum of nickel contains triplet terms.