RT Journal Article SR Electronic T1 Determining Free Sulfur Dioxide in Red Wine JF American Journal of Enology and Viticulture JO Am J Enol Vitic. FD American Society for Enology and Viticulture SP 25 OP 29 DO 10.5344/ajev.1975.26.1.25 VO 26 IS 1 A1 L. F. Burroughs YR 1975 UL http://www.ajevonline.org/content/26/1/25.abstract AB Apparent equilibrium constants were determined for dissociation of the bisulfite addition compounds of malvidin-3-glucoside and of an extract of anthocyanins from a red wine. Normal methods of determining the free SO2 content of wines, which require acidification of the sample, give high results because anthocyanin bisulfites are unstable. The true free SO2 content of red wines can be calculated from the extent to which the natural anthocyanins are decolorized by SO2.