NaCl, sodium chloride, is NaCl whether it comes from the ground, the sea, a laboratory, or outer space. It's the processing (e.g., flaked) or addtional minerals that change it. Ditto for other chemical compounds, including (but not limited to) vitamins.

Actually, saltpeter is KNO3, potassium nitrate. It doesn't do what you think it does when it's put into the mashed potatoes, but it IS a diuretic. It's also an oxidizer, which is why it's used to make black powder (NOT modern "gunpowders", which are nitrocellulose) like Dan'l Boone and Davy Crockett used to shoot b'ars. A close relative is sodium nitrate, which is sometimes used in meats such as hot dogs -- which gives rise to the scenario "Give me the money or I'll light this hot dog and blow us all to hell!"