# Testing Gold the Archimedes Way

I’m sure most people have heard the Archimedes story.He was the Greek guy who got out of his bath tub and ran,naked, down the street,shouting Eureka!Eureka ! I’ve Found It !

Just to refresh memories,here is the story:

What Archimedes had remembered was this:Different metals of the same weight have different volumes. This is because different metals have different densities.Also 0bjects, put in water, will displace water. The displaced water will be equal to their volumes. A metal or alloy that is less dense will displace more water than a denser one.

Using these basic facts, Archimedes worked out a plan to find out the purity of the gold in the crown. He took two bowls and filled them with water to the brim. He then he placed each bowl separately in the middle of 2 other larger vessels. He then placed the crown in one bowl and as the water overflowed he collected the water at the bottom of the outer vessel. Then he took a piece of pure gold,equal in weight to the crown. He put this gold piece in the middle of the second bowl. Here too the  water overflowed and got collected at the bottom of the outer bowl. Archimedes then measured the quantity of water in the two vessels. He found out the difference in the water that overflew in each case. The crown had displaced more water than the pure gold piece.So he concluded that, the gold in the crown had some other metals mixed in it.  Archimedes reported his finding to the King who was then able to wring out a confession from the goldsmith.

This same principle can be  used to determine the purity of gold ,approximately, at home.First weigh the unknown sample. Then determine the water displaced by a known quantity of gold of given purity.Then use ratios to determine how much water a piece of gold of the given purity and the same weight as the unknown sample would displace.If necessary use ratios again to adjust for a different caratage.Here is a worked example on how to do it http://www.chemicalforums.com/index.php?topic=8490.0 .Then compare the amount of water displaced by the unknown sample with what it should theoretically displace and  check the purity of the unknown sample of gold.

This method comes in handy to detect the modern day gold -plated titanium fakes.Titanium is denser than gold and so would displace less water.For more details check this post :http://strats4ever.wordpress.com/2011/02/12/rumours-of-gold-plated-tungsten-how-to-easily-test-yours/ .This is also why it’s safer buying 22k gold over 24k for investment purposes.

### 8 Responses to Testing Gold the Archimedes Way

1. rajesh says:

you did not mentioned when it was discovered

• I don’t know of any such records being present.Do you?

2. Bunny says:

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3. Roho says:

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4. Glen Fitgerald says:

Thank you for a great post.

5. rajendhar says:

too good

6. Ankit says:

Very easy way to understand.Thanks.