What is this close-up picture? (WotsThat: bicarbonate of soda crystals)

Question

What object is shown in this zoomed-in close-up photo?

Accepted Answer

bicarbonate of soda crystals. Bicarbonate of soda was actually used as an early fire extinguisher in the 1920s because when heated, it releases carbon dioxide gas that smothers flames, which is why it still works so effectively on grease fires in your kitchen today. The same chemical reaction that makes it fizz up when you mix it with vinegar is what's been putting out fires for over a century.

Answer: bicarbonate of soda crystals

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