How Iron oxide is made
Hematitite forms naturally when iron-containing rocks and minerals react with oxygen in the air to form iron oxide. The oxide can be made synthetically by a variety of procedures. In the most popular method, iron sulfate is reacted with sodium hydroxide to produce iron hydroxide. The iron hydroxide is then allowed to react with oxygen in the air, forming iron oxide. The compound can also be produced by heating iron sulfate, hydrated iron oxide, or iron oxalate.
Common uses and potential hazards
Iron oxide has been associated with the manufacture of iron and steel for much of human history. The Iron Age, which began in Egypt around 4000 bce was the period in human history when iron was used for tools and weapons. The general approach to refining iron metal from iron ores, such as hematite, was to heat the ore in the presence of carbon. Carbon removes oxygen from the ore, leaving the free metal behind. By the first century bce in China, the first known blast furnaces were in use. In a blast furnace, iron oxide is reduced with carbon by using a blast of air and heat. The oxygen from the air reacts with carbon to give carbon monoxide, which then reacts with iron oxide to produce liquid iron metal and carbon dioxide.
In the eighteenth century, the blast furnace process was further developed so that iron could be made commercially. This process can be traced to the region around Coalbrookdale in Shropshire, England, around the year 1773 and is said to have been a factor in initiating the Industrial Revolution. The blast furnace method is still one of the primary methods by which iron metal is refined from iron ores.
Iron oxide is also one of the oldest known pigments and has been used for that purpose in every major civilization. Some of the best known pigments made from iron oxide have been Indian red, terra Pozzuoli, and Venetian red and have been used to color ceramic glazes and paints. Depending on the exact formulation used, iron oxide produces colors ranging from yellow to orange to red. For example, the hydrated oxide produces a pigment ranging from yellow to brown. Iron oxide pigments have been used as pigment for rubber, paper, linoleum, glass, and many types of paints, including specialty paints used on metalwork and ship hulls.
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