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Gold
Au
atomic number
79
melting point
1064.43 °C

1. Carefully dissolve the powdered sample in concentrated aqua regia, then filter out all the insoluble residues; now carefully evaporate the aqua regia until the sample is completely dry and place it in a test tube; next add a small amount of water and several drops of dilute SnCl2 solution to the sample; the purple precipitate that forms at the bottom of the tube contains colloidal gold and tin hydroxide; the precipitate is soluble in ammonia, coloring the solution red

2. Carefully dissolve the powdered sample in concentrated aqua regia, then filter out the insoluble residues; now place a few drops of the solution on a piece of filter paper and then add a couple of drops of tin chloride "spotting solution" to the sample; dissolved gold is present if a dark brown spot appears; (the spotting solution consists of a small strip of pure tin placed in an eye dropper bottle along with 3 grams of SnCl2 crystals, 25-30 milliliters of water, and 30 drops of dilute HCl)

3. GOLD RECOVERY USING THE FIRE ASSAY (CUPELLATION) TECHNIQUE

4. GOLD RECOVERY USING THE ACID DISSOLUTION TECHNIQUE