By Delos Toole
Select ore samples suspected to contain Gold-Platinum-Palladium and use concentrates equal to the size of one navy bean or pea. Place the concentrates in a clean test tube and add 1cc Nitric Acid and 3cc Hydrochloric Acid, (this a solution named Aqua Regia which is used regularly when testing.) Boil this over a lamp flame for about 5 to 8 minutes. Should this Aqua Regia solution contain Gold-Platinum-Palladium then the following tests will react with various colors, (good idea to practice on known samples of Gold-Platinum-Palladium for color and reaction identification and become familiar to them.)
Test for Gold (Au).
Prepare a solution for Stannous Chloride for each 8 hour period as this solution does not hold up under extended time periods. Dissolving Metallic Tin (Sn) in Hydrochloric Acid (HC1), where the resulted solution will be called Stannous Chloride (SnC1). Place about 2cc of HC1 in a clean test tube and add 1 or 2 small bit pieces of Metallic Tin to the test tube and bring this to a slight boil. You now have Stannous Chloride (SnC1).
Now begin the gold test by making a spot test with freshly made Stannous Chloride by placing a piece of filter paper onto a clean piece of glass and place one drop of Aqua Regia solution in the center of the filter paper, and then add to this mixture one drop of freshly made Stannous Chloride solution. If gold is present there will show up on the filter paper a purple or rose colored spot when the filter paper has dried; the darker the color the more gold will be present; for low grade ore the spot color will appear plainer. Should the filter paper dry out completely, then add 1 more drop of Stannous Chloride solution to the filter paper to bring out the color.
Begin the test for Platinum (Pt) by placing 20 drops of Aqua Regia solution onto a clean porcelain evaporating dish and boil this over a lamp flame until it is dry, then allow this to remain over the lamp flame for about an extended one second.
Place the dish where it can cool for a few minutes so as not to break the dish. After cooling, place 4cc of distilled water, (or water free from Chlorine), and reheat just to the boiling point. Filter this solution onto another clean porcelain evaporating dish. Add to this dish, Potassium Iodide equal to one grain of rice. Warm this solution slightly over the lamp flame and observe the color that appears. The results for this test will show if Platinum (Pt) is present as the solution will begin to turn to a light or dark rose color within a few minutes time.
The more Platinum present in the solution, (ore sample), the quicker and darker the color will appear.
Sulphides and other impurities, most likely will give a red color to the solution and will be mistaken for the rose color, if so, then boil off about one-half of the solution to quicken the evaporation process. Then let the porcelain dish set until completely dry, then add a few drops of clean plain water, (no chlorine water). The result will then be a bright rose color, and should there be Sulphides or other impurities in the solution they will appear as colorless. If this solution should appear red, then add a few cc’s of plain water to dilute the dark rose color to a lighter rose color, then you have Platinum (Pt).
Testing for Palladium(Pd).
In the test for Platinum (Pt), upon adding Potassium Iodide (KI) and warming the procedure, if Palladium (Pd) is present in the sample ore, the solution will turn a dark color or black, which depends upon the amount of Palladium (Pd) present. The more Palladium (Pd) present, the darker the color will be, and also there will be a black precipitate in the bottom of the porcelain dish, which when adding an excess of Potassium Iodide (KI) will dissolve giving a wine-red color appearance.
Delos Toole Copyright 2000.
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