http://docsouth.unc.edu/imls/lecontesalt/leconte.html


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Gunpowder is a mixture of saltpetre (potassium nitrate), charcoal and sulphur. The most critical ingredient is the saltpetre, says Smith, not least because it is by far the largest single constituent. By 1801, saltpetre was being supplied from natural nitrate deposits in India and south-east Asia. But from the mid-14th century until the 1620s — at least 15 years after the plot to blow up parliament — saltpetre was still made in the traditional medieval way, from manure.
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Blast from the past. By: Hamer, Mick, New Scientist, 02624079, 11/5/2005, Vol. 188, Issue 2524