Light green to light brown. Slightly hygroscopic, may cause problems after prolonged storage in hot and humid conditions. If exposed to air and moisture, some FeSO 4 will convert to ferric iron. High free sulfuric acid levels may also cause it to react with other compounds in the feed or mineral mixture. From a feed industry standpoint, the United States is self-sufficient in iron products used in animal teed.
Ferrous sulfate is produced as a by-product of titanium dioxide production.
Titanium dioxide is a pigmenting agent used predominately by the paint industry. A liquid ferrous sulfate sulfuric acid mixture is produced when the atitanium dioxide is extracted from mined ores which contain high iron levels. This mixture is then dried in kilns to produce ferrous sulfate heptahydrate or further dried to produce ferrous sulfate monohydrate. Ferrous sulfate monohydrate is used in a trace mineral premix as the product of choice to supply iron in sulfate form. The possibility of lumped trace mineral premix is substantially reduced but not eliminated when the monohydrate form is used instead of the heptahydrate form.