Disulfurous acid or pyrosulfurous acid is an oxoacid of sulfur with the formula H2S2O5. Its salts are called disulfites or metabisulfites. Disulfurous acid is a phantom acid and does not exist in the free state. Disulfite has two directly connected sulfur atoms. The oxidation state of the sulfur atom bonded to three oxygen atoms is +5, whereas the oxidation number of the other is +3.
Disulfurous acid exhibits a molecular weight of 146.131 g/mol, while its exact mass is 145.934 g/mol. It is prepared via the thermal dehydration of sodium bisulfite or by passing sulfur dioxide over sodium carbonate. Its applications include food preservatives, additives in wines, perfumes, and scents. Disulfurous acid is also commonly used as a reducing agent, besides being employed in easily oxidized pharmaceuticals such as epinephrine hydrochloride and phenylephrine hydrochloride injections, to retard oxidation.
On the basis of geography, the global disulfurous acid market is distributed over North America, Europe, Asia Pacific, Middle East & Africa, and Latin America. The U.S. is expected to propel the disulfurous acid market in North America by accounting for high demand for the product. In Europe, countries such as the U.K., Germany, France, Russia, Spain, Italy, Austria, Netherlands, and Sweden are the leading players. China, South Korea, Japan, India, Thailand, Philippines, Malaysia, and Singapore are likely to dominate the disulfurous acid market in Asia Pacific, with China being a major player. Israel,
Turkey, the U.A.E., Iran, Egypt, Nigeria, Kenya, and Saudi Arabia are some of the leading countries in the market of Middle East & Africa, whereas Latin America is dominated by Brazil, Mexico, and Argentina.The global market comprises numerous companies operating at regional as well as global levels. Key players include Toray Industries, Yara International, PPG Industries, Solvay, Lotte Chemical, DSM, SK Innovation, Shin-Etsu Chemical, Huntsman, Syngenta, Borealis, Lanxess, and Asahi Kasei.