Part V – May 1968 - Papers - The Densities of Some Liquid Lead-Antimony and Lead-Antimony-Tin Alloys

The densities of some liquid Pb-Sb alloys up to 11 wt pct Sb and Pb-Sb-& alloys up to 10 pct Sb/10 pct Sh have been determined by a pycnometric technique over a temperature range of about 130°C above their melting points. The data given are accurate within 0.05 pct. Density is shown to vary linearly with temperature , and equations relating these quantities have been formulated. Molar volumes calculated from the density data indicate that volumetric deviations from ideal mixing are undetectable within the limits of experimental error. A continuing research program into some fundamental physical properties of liquid metals is being pursued at the Mines Branch, Department of Energy, Mines and Resources, Ottawa, Canada. This work has received support from the Canadian Zinc and Lead Research Committee in cooperation with the International Lead and Zinc Research Organization. This paper, which reports some density data for Pb-Sb and Pb-Sb-Sn alloys, follows previous work from this laboratory on lead, tin, and Pb-Sn alloys.' Of previous data from others, Greenaway2 and Sato and Munakata3 have reported results on Pb-Sb alloys. No previous work has been published on the ternary Pb-Sb-Sn alloys, reported here. EXPERIMENTAL METHOD Densities were measured by a pycnometric technique which has been described in detail and appraised for accuracy in earlier Mines Branch reports.475 Fig. 1 shows the densitometer with the pycnometer in position for a run. The pycnometer is also shown in some detail. The pycnometer of dense, high-purity graphite, about 14 cu cm in volume, was carefully machined to a uniform, smooth finish. The height was measured by a depth micrometer and the diameter by fitting precision gage blocks between steel balls.' In each case several readings were taken, and the final results were considered accurate within 0.01 pct. The resulting volumetric uncertainty together with small inaccuracies in the coefficients of linear expansion of graphite lead to a maximum systematic uncertainty in the method of ±0.03 pct. As shown in Fig. 1, the pycnometer lid is a threaded cap. Thus, the charge, a cylinder of the alloy, can easily be inserted and the solidified metal can readily be removed after a run. The dimensions of the cylindrical charge are chosen to ensure that, once molten, the metal will not only fill the pycnometer completely but will discharge an excess into the excess-metal float chamber. AS the temperature is increased above the melting point, the volume of metal in the excess chamber increases until the system has equilibrated at the desired temperature. At this point, the excess chamber is moved to one side by twisting the shaft F, leaving a fixed volume of liquid metal in the pycnometer. This volume of fluid is readily calculated using measured coefficients of linear expansion of the graphite which expands anisotropically. The associated weight of fluid is determined as the weight of the solidified metal removed after the furnace has cooled down. Alloys were prepared from 99.997 pct Pb, 99.999 pct Sn, and 99.999 pct Sb, being melted by an electric furnace in a graphite crucible and poured into graphite molds. Several density specimens of the same nominal size were machined from each ingot, and, by comparing specimen weights, relative differences in specimen composition resulting from segregation in the ingots could be detected. In this way, segregation was found to have occurred in Pb-Sb alloys at compositions beyond the eutectic (11.2 pct Sb) and this