Treated water is tested for impurities including pathogens, nitrates, and nitrites. Nitrates and organic nitrogen compounds can be reduced to ammonia. Other chemical techniques include tests for nitrates, phosphates, sulfates, etc. K-feldspar is particularly susceptible to corrosion by acidic atmospheric pollution such as nitrates and phosphates. Historically, nitric acid was produced by combining sulfuric acid with nitrates such as saltpeter. Sodium tends to form water-soluble compounds, such as halides, sulfates, nitrates, carboxylates and carbonates. Cyanobacteria provide soluble nitrates via nitrogen fixation. These symptoms may be relieved with re-exposure to nitroglycerin or other suitable organic nitrates. Most nitrates and many sulfates are water-soluble. Combustion was traditionally enhanced by addition of potassium or nitrates. Substances involved may include benzocaine, nitrates, or dapsone. Yet, nicorandil is effective in cases where nitrates, such as nitroglycerine, are not effective. The relevant secondary pollutants include peroxylacyl nitrates (PAN), tropospheric ozone, and aldehydes. This is treated by taking aspirin, nitrates, or beta blockers. It is composed of selenium and rhodium nitrates.