Reagent for the colorimetric determination of iron. Base for oxidation-reduction indicator. Alpha-alpha-Dipyridyl solution is used to confirm the presence of ferrous (Fe++) iron in soils. It is used to indicate reducing conditions and the possibility of aquic conditions. Spraying several drops on freshly exposed, uncontaminated soil material will develop a bright pink (or red) color within a few seconds if Fe++ is present at adequate concentration levels. This reaction indicates the soil is reduced and anaerobic at the time of application at least in the area where the reaction occurred. Soil material must be at least moist (usually saturated) for positive reactions to occur.