Crystallographic and bulk properties of platinum from absolute zero to the melting point are assessed from a review of the literature covering the period 1901 to date. Selected values of thermal expansion are used to calculate the variation with temperature of length changes, lattice parameters, inter-atomic distances, atomic and molar volumes, and density. The crystallographic properties are based mainly on the precise dilatometric thermal expansion data, including corrections to account for thermal vacancy effects at the highest temperatures. Literature values are compared graphically with the selected values, and an Appendix is included to explain some of the terms used.
Preview this article: Densities of Osmium and Iridium, Page 1 of 1 < Previous page | Next page > /docserver/preview/fulltext/pmr/33/1/pmr0033-0014-1.gif
Much confusion exists in the literature concerning the densities of osmium and iridium. This has occurred because these values are calculated from crystallographic data, and errors in the absolute value of the X-ray wavelength scale, Avogadro’s Number, and the atomic weights of these elements have only slowly been resolved. Unfortunately density values have been published from time to time which have incorporated one or more of these errors, and these have become fixed in the literature and repeated ever since. The introduction of new values for Avogadro’s Number and the X-ray wavelength scale conversion factor (I), both of which have been used in the present calculations, is an apt moment to review the crystallographic data for these elements and to show that osmium is the densest metal. Avogadro’s Number is now (6.0221367 f 0.0000036) x IO*) per mol while the conversion factor from kX units to Angstrom units is 1.00207789 k 0.00000070. The equivalent Cu Ka , X-ray wavelength standard is then 1.5405945 k O.~II A and an earlier version of this value (I. 540598 A) has already been adopted by the U.S. National Bureau of Standards (2) as a wavelength standard to replace the currently accepted conversion factor of I .00202.
