The final stage in the production of yellow metal is the refining one. Impurities are removed after smelting. The process of refining is executed by help of a furnace or with acid treatment. Most refiners are left with scarp or bars that have to be melted in the furnace. A gold refiner adds soda ash to the metal which is melted to distinguish the pure material from the metals of lesser value.
A jeweler can take on the role of a smelter to purify the metal in-house. There is a possibility that the jeweler would be looking at nuggets in raw form. He or she can place these nuggets within a crucible which is usually built of graphite so that it can survive the high temperatures when the metal is melted.
Once this is done, the aurum recycler can then aim an acetylene torch on the nuggets until they are entirely melted. The molten nuggets are then allowed to harden before treating them with acid. The acids used in this process are concentrated nitric and hydrochloric acids.
The ratio for the addition of acids is 30 ml. For nitric acid and 120 ml. For hydrochloric acid per ounce of the metal. The acids are poured by way of filter funnels in containers such as Pyrex pots. The solution is kept overnight until all the fumes of the acidic reaction are evaporated.
The next step is to add urea and precipitant. The mixture has to be one pound of urea to one quart of heated water. This mixture is added gradually to the acids. A selective gold precipitant is added to a quart of boiling water per ounce of the metal. This is also added slowly to the acids. The solution needs about half an hour to work on the particles.
After the solution works on the metal in the containers, the acid changes to a muddy kind of color. This happens when the metal particles separate. The acid among the dissolved metal is then tested in the lab by the immersion of a stirrer in that acidic solution. Drops of the acid solution are placed on the end of paper towels. The test is carried out by the assayer by dropping a detection liquid particularly for precious metals on the spots on the paper towel. When the color of the solution transforms into a muddy-amber one, then the dissolved metal is well on its way to be refined.
A little tap water is then mixed with the dissolved particles. They have to be rinsed and the extra water is thrown away. The particles go through treatment with aqua ammonia releasing white vapors. Proper protection is warranted against inhaling these vapors by wearing protective gear like a face mask and goggles.
The metal particles are placed in a beaker once the draining of the distilled water is over. The gold refiner allows the beaker to slowly heat on a hot plate till the metal particles transform into powder dust. This dust is then removed on multiple layers of paper towel. It is then wrapped carefully in those towels before being soaked in alcohol. After they are dried again, they are poured again into a graphite crucible to be melted again to attain form purity.
A jeweler can take on the role of a smelter to purify the metal in-house. There is a possibility that the jeweler would be looking at nuggets in raw form. He or she can place these nuggets within a crucible which is usually built of graphite so that it can survive the high temperatures when the metal is melted.
Once this is done, the aurum recycler can then aim an acetylene torch on the nuggets until they are entirely melted. The molten nuggets are then allowed to harden before treating them with acid. The acids used in this process are concentrated nitric and hydrochloric acids.
The ratio for the addition of acids is 30 ml. For nitric acid and 120 ml. For hydrochloric acid per ounce of the metal. The acids are poured by way of filter funnels in containers such as Pyrex pots. The solution is kept overnight until all the fumes of the acidic reaction are evaporated.
The next step is to add urea and precipitant. The mixture has to be one pound of urea to one quart of heated water. This mixture is added gradually to the acids. A selective gold precipitant is added to a quart of boiling water per ounce of the metal. This is also added slowly to the acids. The solution needs about half an hour to work on the particles.
After the solution works on the metal in the containers, the acid changes to a muddy kind of color. This happens when the metal particles separate. The acid among the dissolved metal is then tested in the lab by the immersion of a stirrer in that acidic solution. Drops of the acid solution are placed on the end of paper towels. The test is carried out by the assayer by dropping a detection liquid particularly for precious metals on the spots on the paper towel. When the color of the solution transforms into a muddy-amber one, then the dissolved metal is well on its way to be refined.
A little tap water is then mixed with the dissolved particles. They have to be rinsed and the extra water is thrown away. The particles go through treatment with aqua ammonia releasing white vapors. Proper protection is warranted against inhaling these vapors by wearing protective gear like a face mask and goggles.
The metal particles are placed in a beaker once the draining of the distilled water is over. The gold refiner allows the beaker to slowly heat on a hot plate till the metal particles transform into powder dust. This dust is then removed on multiple layers of paper towel. It is then wrapped carefully in those towels before being soaked in alcohol. After they are dried again, they are poured again into a graphite crucible to be melted again to attain form purity.
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