High accuracy measurement of gold purity using hydrostatic weighing system

Abstract

Currently, existing instruments have limitation to determine the purity of gold bar and the method used is not reliable to detect the existence of tungsten in bar. Therefore, a new technique with high accuracy and non-destructive method has been developed to determine the purity of gold bar. In this study, three approaches were considered in the construction of hydrostatic weighing system (HWS); establishment of location and environmental condition, establishment of the density measurement of distilled water and establishment the mass measurement of samples. The X-ray fluorescence (XRF) analysis was used to determine the surface purity, while the HWS was used to determine the density of gold bar. The standard sample of gold bar, tungsten bar and fake gold bar were used in this study. Experimental results show that the density of gold bar is proportional to the purity of gold bar. The purity of 99.99% and 99.9% gold has density of 19.293 g/ml and 19.268 g/ml respectively. However, for tungsten, the density of 99.9% tungsten was only 19.206 g/ml with the expanded uncertainty of the density of 0.006 g/ml. Thus, this study demonstrates that the developed HWS is capable to be used to measure the density of gold bar accurately and hence it could detect the presence of tungsten in gold bar.