How to refine gold plating

Written by chuck ayers
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How to refine gold plating
Use a glass wand to stir the chemicals for reverse electrolysis. (chemical glassware image by Oleg Mitiukhin from Fotolia.com)

Refining gold plating takes two steps. The first step involves reverse electrolysis to remove the gold from the plated item. Electrolysis is an electrical process where the negatively charged ions from the gold adhere themselves to the positively charged ions of another metal or material. To reverse the process, you will want the positively charge the gold plating so that it will be attracted to the negatively charged ions in another material -- often silver but for this process it will be stainless steel. To allow the transference, it must occur in an electrolyte solution.

Skill level:
Easy

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Things you need

  • Protective clothing
  • Glass beaker
  • Glass wand
  • Gold plated material
  • A 9 volt or 12 volt battery
  • Two glass beakers
  • Two alligator clips
  • Copper wire
  • A stainless steel metal rod
  • Electrolyte solution of sodium cyanide,sodium hydroxide andsodium-meta nitro benzene sulphonate
  • Aqua regia

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Instructions

  1. 1

    Collect all the gold plated material you want to refine to 24 carat gold. This can include the circuit boards of old 386 or 486 computers, old analogue cell phones, stereo cables, jewellery and any other materials that have been gold plated. Gold's high electrical conductivity makes it attractive to sparing use at critical circuit junctions but its price limits its use.

  2. 2

    Prepare an electrolyte solution in a glass beaker consisting of 70 per cent sodium cyanide (NaCN), 15 per cent sodium hydroxide (NaOH) and 15 per cent sodium-meta nitro benzene sulphonate. This will serve as a chemical bath conductor to better facilitate the free-flow of ions from the gold-plated material. Use a glass wand to stir the mixture thoroughly.

  3. 3

    Prepare your electrical source. Either a 9 volt of 12 volt battery is satisfactory. Clean and attach a small alligator clip on one end of each of two 9-inch wires. Connect the opposite end of one wire to the positive end of the battery and the end of the other wire to the negative end of the battery. Attach the alligator clamp from the positive wire to the collected scrap gold and gently lower the gold scrap into the beaker containing the electrolyte solution. Connect the alligator clamp attached to the negative end of the battery to the steel post and slowly introduce the steel post into the electrolyte solution, letting it come to rest at the bottom of the beaker. Basically, you're creating a circuit that will flow through the electrolyte solution transferring the positively charged gold ions to the negatively charged steel anadode.

  4. 4

    Wait for the low volt charge to do its work. It will take a little while to positively charge the gold-plated materials and generate current sufficient enough to carry it to the ions to the negatively charged steel anode. The amount of removed gold plating adhering to the anode can be measured in microns (basically because you're using small amounts of plating and the low electric current). And will take time to accumulate on the anadode. Over a period of time the gold adhering to the anode will thicken and can be scraped off when the process is complete.

  5. 5

    Repeat this process with all the gold plated material you wish to render. Along with the gold, however, came impurities rendering the gold somewhere between 12 carat and 18 Karat gold. To refine the gold further and remove the impurities requires another step to make it 99.99 per cent pure or 24 carat gold.

  6. 6

    Fill a separate glass beaker halfway with aqua regia, which is a mixture of nitrohydrochloric acid hydrochloric acid. Gently introduce the gold into the solution and fill the beaker with sodium meta bisulphite and stir gently with a glass wand. No splashing. The impurities will dissolve and the 24K gold will settle to the bottom of the beaker. Drain the solution as much as possible without splashing or pouring off the refined gold and allow the gold to dry. Wash the gold thoroughly with water and you've reversed the electroplating process and have the pure gold that was used from the start (or perhaps even more pure).

Tips and warnings

  • The price of gold topped £650 per ounce in late 2010 so the time and money invested in recovering gold plating and refining it could be well worth the effort. Those old computer circuit boards you may have considered throwing away may have a significant value, though not as a computer.
  • The fluids for this process are extremely caustic, including the fumes they create when mixed. Wear protective leather or rubber outerwear and gloves and use a respirator to avoid inhaling the fumes. Work in a well ventilated area.

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