Verification of the hydrostatic weighing system with existing gold purity instruments

Abstract

Determination of gold bar purity remains one of the most challenging tasks in gold industry. Currently, the existing instruments have a limitation to determine the purity, which in turn have produced inaccurate gold purity measurement. For example, X-ray fluorescence (XRF) technique has a limitation to penetrate the gold bar and XRF was only used to determine the surface purity. Therefore, an improved non-destructive method and precise technique has been developed to determine the gold purity. Gold density measurement can verify the purity of the gold and in this study, the density of gold bar was calculated using a custom made hydrostatic weighing system (HWS). Several measurements of density were carried out for gold bar and tungsten bar. Using HWS, the density of gold bar and tungsten bar were 19.268 g/ml and 19.206 g/ml respectively. The expanded uncertainty was also evaluated and the value was 0.006 g/ml. The new developed HWS method was also verified with existing density measurement instruments where the same density results has been obtained but the existing instruments have produced bigger uncertainty of 0.2 g/ml. Thus, this study demonstrates that the developed HWS is appropriate to be used to measure the density of gold bar accurately. Furthermore, the new developed system of HWS have shown better measurement with smaller uncertainty and hence the improvement in gold bar purity measurement.