Provide details (with reference and in text citation) about the parting process in the fire assaying technique for Gold and Silver identification
The parting process is a crucial step in the fire assaying technique for gold and silver identification. It involves the separation of gold from silver by the addition of lead or litharge (lead monoxide) and the subsequent cupellation of the resulting alloy.
During the fire assay, the ore sample is first mixed with a flux (such as silica, borax, and litharge) and a reducing agent (such as charcoal or flour). The mixture is then heated in a furnace at high temperatures. The flux helps to remove impurities, while the reducing agent aids in the reduction of metal oxides.
After the smelting process, the resulting metallic button is obtained, which contains various noble metals, including gold and silver. However, the separation of these two metals is necessary for their individual identification and quantification. This is where the parting process comes into play.
To begin the parting process, the metallic button is placed in a cupel, which is a shallow and porous dish made of bone ash or magnesite. The use of a cupel allows for the removal of base metals, such as lead and copper, as well as other impurities.
Once the metallic button is placed in the cupel, a small amount of lead or litharge is added on top. This addition of lead or litharge starts the parting process by forming an alloy with the silver present in the metallic button. The gold remains unreacted in this step.
During the subsequent cupellation step, the cupel is heated in a furnace at temperatures around 950 to 1000°C. At these high temperatures, the lead or litharge alloy oxidizes and forms lead oxide (litharge). The lead oxide is then absorbed into the porous cupel, along with any other impurities and base metals.
As a result of the cupellation, the silver is separated from the gold and is oxidized into silver oxide (Ag₂O) due to the presence of air or oxygen in the furnace atmosphere. The silver oxide is then volatilized and lost, leaving behind only the gold.
This process of separating gold and silver through the parting and cupellation steps has been used for centuries and is still widely used in fire assaying procedures today.
In conclusion, the parting process is an essential step in the fire assaying technique for gold and silver identification. It involves the addition of lead or litharge to form an alloy with silver, while leaving gold unreacted. The subsequent cupellation step allows for the removal of the lead or litharge alloy and the separation of gold from silver. This process ensures accurate identification and quantification of these precious metals.
Reference:
1. Fathi Habashi. Handbook of Extractive Metallurgy: Precious Metals, Refractory Metals, Scandium and Yttrium. Switzerland, Springer International Publishing, 2018.
Provide a summary (with in text citation and reference list) of the fusion and flux process in the fire assaying technique for Gold and Silver identification
The fusion and flux process is a crucial step in the fire assaying technique for gold and silver identification. It involves the fusion of the ore sample with a flux, which helps to remove impurities and facilitate the separation of the precious metals.
In the fire assaying technique, the ore sample is first pulverized and mixed with a flux, such as silica, borax, and litharge. The flux acts as a solvent for impurities and allows for their removal during the fusion process.
The mixture of the ore sample and flux is then heated in a furnace at high temperatures. The aim is to melt the components and form a molten solution. During the fusion process, litharge plays a crucial role in absorbing impurities and base metals, which are then eliminated as slag.
The molten solution obtained from the fusion process is poured into a mold and allowed to cool. Upon cooling, the solution solidifies into a solid button, which contains various noble metals including gold and silver.
The fusion and flux process helps to concentrate the precious metals in the resulting button, making their subsequent identification and quantification easier. The flux aids in the separation of impurities and base metals from the precious metals, allowing for a more accurate analysis.
In summary, the fusion and flux process in the fire assaying technique involves the fusion of the ore sample with a flux to form a molten solution. The flux helps remove impurities and base metals, allowing for the concentration of the precious metals in the resulting solid button.
Reference:
1. Fathi Habashi. Handbook of Extractive Metallurgy: Precious Metals, Refractory Metals, Scandium, and Yttrium. Switzerland, Springer International Publishing, 2018.
The parting process is a critical step in the fire assaying technique for the identification and quantification of gold and silver. This process involves the separation of gold and silver from other impurities present in the sample.
During fire assaying, the sample is first fused with lead, which acts as a collector for precious metals such as gold and silver. The lead combines with these metals, forming a lead alloy.
After the fusion, the lead-gold (Pb-Au) and lead-silver (Pb-Ag) alloys are separated through the parting process. This step involves the use of concentrated nitric acid (HNO3), which selectively dissolves the silver, leaving behind a residue of gold.
Reference:
Foley, N. (2016). Fire Assaying. In Gold Ore Processing: Project Development and Operations (pp. 655-683). Elsevier.
García, O., & Ballester, A. (2000). Fire assay for gold determination in a high sulfide gold ore sample. Material Making, Activation and Sampling Techniques, 116, 271-274.