Saltpeter is a common chemical, used for many products and science projects. Here's a look at what exactly saltpeter is. Answer: Saltpeter is the natural mineral source of the chemical potassium nitrate, KNO 3. Depending where you live, it may be spelled 'saltpetre' rather than 'saltpeter'.Before systematic naming of chemicals, saltpeter was called nitrate of potash. It has also been called 'Chinese salt' or 'Chinese snow'.Pure saltpeter or potassium nitrate is a white crystalline solid, usually encountered as a powder. Most potassium nitrate is produced using chemical reaction of nitric acid and potassium salts, but bat guano was an important historical natural source.altpeter is a common chemical, used for many products and science projects. Here's a look at what exactly saltpeter is. Answer: Saltpeter is the natural mineral source of the chemical potassium nitrate, KNO 3. Depending where you live, it may be spelled 'saltpetre' rather than 'saltpeter'.