Gravimetry is an old technique which has been used for the determination and recovery of gold ever since its discovery. It is a process that has a minimal room for instrumental error and does not require standards for any calculation of the unknown that is being analyzed. The determination of gold besides gravimetry can either be titrimetry or instrumental, but these techniques requires gold standards for comparison of its results and concerns the determination of gold in small scale or trace amounts like that of atomic absorption spectroscopy (AAS). The demand for gold is rapidly icreasing world wide and as of today, the standard test for its determination is Fire Assay ASTM E 1335-08 – a ...view middle of the document...
A G-4 crucible was used to dry the precipitate and the difference between the final and initial weight were used to calculate the total amount of gold. The researchers used reactions (1) and (2) as their guideline
Au + 3HNO3 + 4HCl -> 3H2O + HAuCl4 + 3NO2 (1)
HAuCl4 + NH2OH.HCl -> Au + NH4OH + 5Cl (2)
In adiition, a calculation of the concentration and uncertainties present in atomic mass, repeatability (3), and weighing (4) of gold was done basing from the guidelines of the Ishkawa diagram – a figure showing sources of uncertainty in the determination of gold by gravimetry.
Where C(MAu) is the concentration of gold in percent; Wsamp weight of gold sample; Wau wight of precipitate
All of the calculated results showed very significant values particularly the percentage of purity which was found out to be 99.993 ± 0.0056 with 95% confidence level (k=2). This purity level is an excellent result since metallic impurities are very much present in gold samples particulary in this study wherein the presence of Sn or Pb determines the acid to be used, but with the use of aqua regia (HNO3/HCL) these impurities were negligible for the estimation on the amount of gold due to its selective reduction property (for gold). One of the main inteference was the presence of high concentration of silver in the gold sample. It was treated by nitric acid because silver is highly soluble in HNO3 while gold on the other hand is insoluble. After the collection of the precipitate from acid digestion, the gold precipitate were washed with 10%...