Iodine dropping method: drop a small amount of Sodium Metabisulfite solution into the water containing starch. If blue or black pigment appears, it means that Sodium Metabisulfite contains iodine ions.
Chlorine ion detection method: add Sodium Metabisulfite solution to silver chloride solution. If there is white precipitation, it means that Sodium Metabisulfite contains chlorine ion.
Sulfate ion detection method: add Sodium Metabisulfite solution to silver nitrate solution. If there is white precipitation, it means that Sodium Metabisulfite contains sulfate ion.
Colorimetry: measure the absorbance of Sodium Metabisulfite solution with ultraviolet visible spectrometer or spectrophotometer, and calculate the concentration of Sodium Metabisulfite according to the relationship between absorbance and concentration.
