The potassium nitrate

The most important part of the black gunpowder is the potassium nitrate KNO3. For many centuries, potassium nitrate was extracted by washing the soil.

The most important part of the black gunpowder is the potassium nitrate

After the revolution of 1789, France was in a strong siege ring. British in the Sea, austrians and germans in the land is not passed to the French territory of any ship or convoy with potassium nitrate. The revolutionary government ordered the " wash the land of their cellars, stables, corrals and barns". The potassium nitrate was the most necessary material for the whole of France. But still, how to extract from the soil the potassium nitrate?

In the stables, barns, urine leaks all the time, and nitrogen-containing excrement. Ammonia that is thus formed is oxidized by microorganisms to to nitric acid. The nitrate acid forms with soil nitrates and carbonates of calcium nitrate. The soil is first washed with hot water, then filtered and thereafter filtrate was added to potassium:

Ca(NO3)2 + K2CO3 = CaCO3 + 2KNO3.

The potassium nitrate solution separated from the precipitate and evaporated to crystallization. Potassium nitrate crystals obtained were purified by recrystallization.

Sometimes the potassium nitrate extracted from the earth so called saltpeter "deposits". It was a pile of different waste, feces, pus, debris, mixed with limestone or lime. After digestion of these mixtures of the calcium nitrate was washed out, the reaction product with K2CO3 was potassium nitrate.