You can stop puzzling over what to do with those unwanted recordable CDs. Researchers at the University of São Paulo in Brazil have developed a way to make electrodes out of the pre-polished gold that lines them. Using nitric acid, they removed the CD's plastic layers to reveal the gold layer, which is about 50 to 100 nanometres thick. The gold is the perfect thickness for use in many types of electrolytic cellsparticularly those used to measure levels of mercury and copper in drinking water.
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