Black powder made with less-expensive and more plentiful sodium nitrate (in appropriate proportions) works just as well but is more hygroscopic than powders made from potassium nitrate--popularly known as saltpeter.
Black powder made with less-expensive and more plentiful sodium nitrate (in appropriate proportions) works just as well, and previous equations apply, with sodium instead of potassium. However, it is more hygroscopic than powders made from potassium nitrate--popularly known as saltpeter.