Some reading on Sulfur production by the South during the Civil War:
http://civilwartalk.com/threads/how...tain-sulpher-for-gunpowder-manufacture.96029/
They used nitric acid to leach sulfur from iron pyrite.
https://books.google.co.uk/books?id... sulphur from iron pyrite confederate&f=false
Another mention of refining sulfur:
Seems to me that the making BP from non-commercially procured ingredients take knowledge of history and chemistry.
http://civilwartalk.com/threads/how...tain-sulpher-for-gunpowder-manufacture.96029/
They used nitric acid to leach sulfur from iron pyrite.
https://books.google.co.uk/books?id... sulphur from iron pyrite confederate&f=false
Another mention of refining sulfur:
http://civilwartalk.com/threads/black-powder-without-sulfur.96740/
Seems to me that the making BP from non-commercially procured ingredients take knowledge of history and chemistry.