Question

what is maen by potassium nitrate​

Answer 1

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: a crystalline salt KNO3 that occurs as a product of nitrification in arable soils, is a strong oxidizer, and is used especially in making gunpowder, as a fertilizer, and in medicine.

Answer 2

It is a source of nitrogen, and nitrogen was named after niter. Potassium nitrate is one of several nitrogen-containing compounds collectively referred to as saltpeter (or saltpetre in the UK).

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Potassium nitrate