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Jake Jennings, Kentucky asked:
Why is it that when beer has gone flat, the fizz seems to come back when you add some salt? It there a chemical reaction at work?
Even when it looks like a drink has gone flat, there’s still a lot of carbon dioxide dissolved in it. Sprinkling salt or sugar in the drink will create lots of 'nucleation' sites on which bubbles can form, so some fizz will come back.