Hematite Fe 2 O 3 based trigonal system, corundum type structure belongs, there are two crystalline forms, i.e., α-Fe 2 O 3 (hematite) and α-Fe 2 O 3 (maghemite). The transition temperatures of these two different crystal forms are approximately 400 ° C. γ-Fe 2 O 3 is thermodynamically unstable and is in a metastable state, and will change to α-Fe 2 O 3 at around 400 °C. Natural hematite α-Fe 2 O 3 is mainly a weathered product of iron-containing silicates, sulfides and carbonates and is the most stable iron compound in the natural environment. The first product obtained by heating the iron hydroxide isolated from the low-temperature solution water is iron oxide monohydrate, which is goethite, and then hemihydrate iron oxide, which is hemihydrate, and further heated to obtain α-type Fe 2 O 3 . The transition temperature of goethite and gamma-type Fe 2 O 3 is approximately 160 ° C. If a high-temperature hydrolysis method is employed, as the hydrolysis temperature is continuously increased, one water, half water, and anhydrous ferric oxide can be sequentially obtained. A pyrite process for high temperature hydrolysis in the industry for precipitating iron. The higher the temperature, the faster the hydrolysis rate, and the better the precipitation of iron at higher acidity. At a high temperature of 200 ° C, even if the sulfuric acid concentration is as high as 100 kg ∕ m 3 , the residual iron concentration in the solution can be reduced to 5-6 kg ∕m 3 . Iron Oxide Pigment ,Red Iron Oxide,Iron Oxide Powder,Yellow Oxide Wenzhou Jinbaicai Pigment Co.,Ltd , https://www.jbcbsdpigment.com