The chemicals react, and their products duly register in a nearby computer.

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These free radicals are oxygen-rich molecules in which one of the oxygen atoms is particularly likely to react with other chemicals.

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These are tiny glass chips dotted with thousands of microscopic wells where DNA fragments react with other chemicals in order to measure the activity of genes or identify genetic variations.

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These react with CO2 to form soluble chemicals called carbamates and bicarbonates.

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Most of those chemicals are designed to stay underground, where they react with the rock and help the oil and gas flow.

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Only a few polymers, however, conduct electricity, and so the range of chemicals that can be detected is limited to those that will react with those polymers.

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