Monday, January 13, 2014

Turn Water into Liquid Gold

Mix two clear solutions, wait, and watch the liquid turn to gold! This is a simple alchemy project or chemistry demonstration, based on early attempts to make gold from base metals.

 

 

Liquid Gold Materials

Solution A
  • 1 gram sodium arsenite
  • 50 ml water
  • 5.5 ml glacial acetic acid
Prepare Solution A by stirring the sodium arsenite into the water. Mix the glacial acetic acid into this solution. Solution B
  • 10 grams sodium thiosulfate (photographer hypo)
  • 50 ml water
Prepare Solution B by stirring the sodium thiosulfate into the water.

Let's Make Liquid Gold!

Pour one solution into the other. The clear solution will turn gold after about 30 seconds. For dramatic effect, keep track of the time and command the solution to turn into gold. You can even use a magic word, if you like.

The Chemistry Behind How It Works

There is a delayed reaction between the acid and the sodium thiosulfate to release hydrogen sulfide gas. The hydrogen sulfide reacts in turn with sodium arsenite to precipitate tiny crystals of golden arsenious sulfide, which is also known as arsenic trisulfide (As2S3) or orpiment. Both Western and Chinese alchemists experimented with orpiment to try to make gold. Although the mineral can be made to appear metallic under certain conditions, the compound does not undergo any reaction which changes either the arsenic or the sulfur into gold. It's a striking demonstration though!

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