The gunpowder is only a simple mix of sulphur, charcoal and saltpeter, but it is known how much it influenced our history. Well, among the three ingredients, the last was the hardest to obtain until the 20th century. Derived as name from the Latin sal petrae (salt of the rock), the saltpeter is a nitrate salt (of calcium, potasium or sodium), used also as fertilizer and food preservative. The calcium nitrate (Norwegian saltpeter) forms an efflorescence where the manure comes in contact with the limestone in a dry environment as in stables or caverns. The potassium nitrate (niter, Chinese snow, or India salpeter) occurs also as a crust on the soil and on the surface of rocks in dry climates and in the soil of limestone caves. Both were therefore rare. In this context, you realize what it meant to Chile and Peru the discovery in the Atacama desert of some deposits of sodium nitrate (nitranite) covering immense areas. The accumulations were so big, that this mineral was named Chile saltpeter or Peru saltpeter.
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