Investing in gold: Using science to check metal's purity

An ultrasound device (above) is used to check the purity of each gold bar and to ensure gilded tungsten, which has a very similar density to gold, is not passed off as the precious metal. Gold purity is also tested with a spectrometer, which emits a special X-ray to analyse the metal content of the bar and flag any adulteration. ST PHOTOS: LIM YAOHUI
Each bar of gold is precisely cast at 1kg and, like a currency note, each of them has a unique serial number. ST PHOTOS: LIM YAOHUI
An ultrasound device is used to check the purity of each gold bar and to ensure gilded tungsten, which has a very similar density to gold, is not passed off as the precious metal. Gold purity is also tested with a spectrometer (above), which emits a special X-ray to analyse the metal content of the bar and flag any adulteration. ST PHOTOS: LIM YAOHUI
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How do you know whether a gold bar is pure or mixed with impurities?

After all, you may think that in a shipment of multiple gold bullion, it may be easy to slip in a dud or two to fool the purchaser.

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A version of this article appeared in the print edition of The Sunday Times on November 15, 2020, with the headline Investing in gold: Using science to check metal's purity. Subscribe