The density of any point p in an object is defined as:
M is the mass of the volume element. In the centimeter-gram-second system, the unit of density is gram/cubic centimeter; In the international system of units and China's legal units of measurement, the unit of density is kg/m3.
There are many kinds of iron ores, among which magnetite (Fe3O4), hematite (Fe2O3) and siderite (FeCO3) are mainly used for ironmaking. After the iron ore sample is dissolved with hydrochloric acid, the iron in it is transformed into Fe3+. Under the condition of strong acid, Fe3+ can be reduced to Fe2+ through SnCl2.
After Fe3+ is reduced by Sn2+, methyl orange can also be reduced to hydrogenated methyl orange by Sn2+ and fade, so methyl orange can indicate the end point of Fe3+ reduction. Sn2+ can continue to reduce hydrogenated methyl orange to N, N- dimethyl p-phenylenediamine and sodium p-aminobenzene sulfonate.
Extended data
Beneficial and harmful elements:
Beneficial and unhelpful elements in iron ore: There are many impurities in iron ore, which can be divided into beneficial and harmful according to their influence on smelting process and product quality.
1. harmful impurities (elements)
Refers to impurities that affect mineral processing and smelting. Common and main harmful impurities are: sulfur, phosphorus, arsenic, potassium, sodium, fluorine and so on.
(1) phosphorus
Phosphorus is generally apatite (3CaO? P2O5) state, with blue iron ore (3FeO? As3O5) state exists. Phosphorus is completely reduced in blast furnace, and most of it goes into pig iron. Steel with high phosphorus content is easy to break when processed at low temperature, which is called "cold brittleness".
(2) Sulfur
Sulfur mainly exists in pyrite (FeS2), chalcopyrite (FeS, CuS) or sulfate (CaSO4.2H2O \ BaSO4). Sulfur is partially reduced to pig iron during smelting, and sulfur in steel is easy to produce "hot brittleness" during hot working. Although desulfurization can be carried out in blast furnace smelting, it will consume more coke (increasing furnace temperature) and limestone (increasing slag alkalinity), and even increase production costs. Therefore, the iron ore charged into the furnace needs sulfur content.
(3) Potassium and sodium
It is often found in aegirine, sodium amphibole and marble. Their biggest harm is to reduce the softening point of iron ore, which often leads to nodulation in blast furnace. Minerals with high potassium and sodium content often affect the smooth smelting of blast furnace.
(4) Arsenic
Arsenic is rare in general iron ore, but common in limonite. It exists in the form of arsenopyrite (FeAs2S) or other oxides (As2O3, As3O5). Most arsenic enters pig iron during smelting. When the arsenic content in steel exceeds 0. 1%, it will make steel cold brittle and affect the weldability of steel.
2. beneficial elements (impurity)
Some elements in iron ore may be unfavorable to smelting process, but they can often improve some properties of products. We call it beneficial elements. Such common elements are: manganese, nickel, chromium, vanadium, titanium and so on.
Baidu encyclopedia-iron ore