The test paper allows the rapid detection of sulfite and sulfur dioxide. The paper is used in food analyzing laboratories. The reaction is as follows:
2 IO3– + 5 SO32– + 2 H+ → 5 SO42– + I2 + H2O
Sulfurous acid or sulfites reduce potassium iodate to free iodine. With starch, iodine gives a characteristic blue-black color. For a detection of sulptie with high sensitivity we recommend Sulfite Test paper (REF 907 63).