Sulfuric acid or sulphuric acid, known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, and hydrogen, with the molecular formula H2SO4. It is a colorless, odorless, and viscous liquid that is soluble with water.
In chemistry, iron(II) refers to the element iron in its +2 oxidation state. The adjective ferrous or the prefix ferro- is often used to specify such compounds, as in ferrous chloride for iron(II) chloride (FeCl2). The adjective ferric is used instead for iron(III) salts, containing the cation Fe3+. The word ferrous is derived from the Latin word ferrum, meaning "iron".
Iron(II) sulfate (British English: iron(II) sulphate) or ferrous sulfate denotes a range of salts with the formula FeSO4·xH2O. These compounds exist most commonly as the heptahydrate (x = 7) but several values for x are known. The hydrated form is used medically to treat or prevent iron deficiency, and also for industrial applications. Known since ancient times as copperas and as green vitriol (vitriol is an archaic name for hydrated sulfate minerals), the blue-green heptahydrate (hydrate with 7 molecules of water) is the most common form of this material. All the iron(II) sulfates dissolve in water to give the same aquo complex [Fe(H2O)6]2+, which has octahedral molecular geometry and is paramagnetic. The name copperas dates from times when the copper(II) sulfate was known as blue copperas, and perhaps in analogy, iron(II) and zinc sulfate were known respectively as green and white copperas.
Iron(III) chloride describes the inorganic compounds with the formula FeCl3(H2O)x. Also called ferric chloride, these compounds are some of the most important and commonplace compounds of iron. They are available both in anhydrous and in hydrated forms, which are both hygroscopic. They feature iron in its +3 oxidation state. The anhydrous derivative is a Lewis acid, while all forms are mild oxidizing agents. It is used as a water cleaner and as an etchant for metals.
In environmental chemistry, the chemical oxygen demand (COD) is an indicative measure of the amount of oxygen that can be consumed by reactions in a measured solution. It is commonly expressed in mass of oxygen consumed over volume of solution, which in SI units is milligrams per liter (mg/L). A COD test can be used to quickly quantify the amount of organics in water. The most common application of COD is in quantifying the amount of oxidizable pollutants found in surface water or wastewater. COD is useful in terms of water quality by providing a metric to determine the effect an effluent will have on the receiving body, much like biochemical oxygen demand (BOD).
Iron (II) hydroxide or ferrous hydroxide is an inorganic compound with the formula Fe(OH)2. It is produced when iron (II) salts, from a compound such as iron(II) sulfate, are treated with hydroxide ions. Iron(II) hydroxide is a white solid, but even traces of oxygen impart a greenish tinge. The air-oxidised solid is sometimes known as "green rust".
A double salt is a salt that contains two or more different cations or anions. Examples of double salts include alums (with the general formula MIMIII(SO4)2·12H2O) and Tutton's salts (with the general formula (MI)2MII(SO4)2·6H2O). Other examples include potassium sodium tartrate, ammonium iron(II) sulfate (Mohr's salt), potassium uranyl sulfate (used to discover radioactivity) and bromlite BaCa(CO3)2. The fluorocarbonates contain fluoride and carbonate anions. Many coordination complexes form double salts.
Indium(III) sulfate (In2(SO4)3) is a sulfate salt of the metal indium. It is a sesquisulfate, meaning that the sulfate group occurs 11/2 times as much as the metal. It may be formed by the reaction of indium, its oxide, or its carbonate with sulfuric acid. An excess of strong acid is required, otherwise insoluble basic salts are formed. As a solid indium sulfate can be anhydrous, or take the form of a pentahydrate with five water molecules or a nonahydrate with nine molecules of water. Indium sulfate is used in the production of indium or indium containing substances. Indium sulfate also can be found in basic salts, acidic salts or double salts including indium alum.
Iron shows the characteristic chemical properties of the transition metals, namely the ability to form variable oxidation states differing by steps of one and a very large coordination and organometallic chemistry: indeed, it was the discovery of an iron compound, ferrocene, that revolutionalized the latter field in the 1950s. Iron is sometimes considered as a prototype for the entire block of transition metals, due to its abundance and the immense role it has played in the technological progress of humanity. Its 26 electrons are arranged in the configuration [Ar]3d64s2, of which the 3d and 4s electrons are relatively close in energy, and thus it can lose a variable number of electrons and there is no clear point where further ionization becomes unprofitable.
Ammonium iron(II) sulfate, or Mohr's salt, is the inorganic compound with the formula (NH4)2SO4.Fe(SO4).6H2O. Containing two different cations, Fe2+ and NH+4, it is classified as a double salt of ferrous sulfate and ammonium sulfate. It is a common laboratory reagent because it is readily crystallized, and crystals resist oxidation by air. Like the other ferrous sulfate salts, ferrous ammonium sulfate dissolves in water to give the aquo complex [Fe(H2O)6]2+, which has octahedral molecular geometry. Its mineral form is mohrite.
Szomolnokite (Fe2+SO4·H2O) is a monoclinic iron sulfate mineral forming a complete solid solution with magnesium end-member kieserite (MgSO4·H2O). In 1877 szomolnokite's name was derived by Joseph Krenner from its type locality of oxidized sulfide ore containing iron in Szomolnok, Slovakia (Hungary at the time).
Iron(III) sulfate (or ferric sulfate), is a family of inorganic compounds with the formula Fe2(SO4)3(H2O)n. A variety of hydrates are known, including the most commonly encountered form of "ferric sulfate". Solutions are used in dyeing as a mordant, and as a coagulant for industrial wastes. Solutions of ferric sulfate are also used in the processing of aluminum and steel.
Tutton's salts are a family of salts with the formula M2M'(SO4)2(H2O)6 (sulfates) or M2M'(SeO4)2(H2O)6 (selenates). These materials are double salts, which means that they contain two different cations, M+ and M'2+ crystallized in the same regular ionic lattice. The univalent cation can be potassium, rubidium, caesium, ammonium (NH4), deuterated ammonium (ND4) or thallium. Sodium or lithium ions are too small. The divalent cation can be magnesium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc or cadmium. In addition to sulfate and selenate, the divalent anion can be chromate (CrO42−), tetrafluoroberyllate (BeF42−), hydrogenphosphate (HPO42−) or monofluorophosphate (PO3F2−). Tutton's salts crystallize in the monoclinic space group P21/a. The robustness is the result of the complementary hydrogen-bonding between the tetrahedral anions and cations as well their interactions with the metal aquo complex [M(H2O)6]2+.
Ferrous citrate, also known as iron(II) citrate or iron(2+) citrate, describes coordination complexes containing citrate anions with Fe2+ formed in aqueous solution. Although a number of complexes are possible (or even likely), only one complex has been crystallized. That complex is the coordination polymer with the formula [Fe(H2O)6]2+{[Fe(C6H5O7)(H2O)]−}2.2H2O, where C6H5O73- is HOC(CH2CO2−)2(CO2−, i.e., the triple conjugate base of citric acid wherein the three carboxylic acid groups are ionized. Ferrous citrates are all paramagnetic, reflecting the weak crystal field of the carboxylate ligands.
Green rust is a generic name for various green crystalline chemical compounds containing iron(II) and iron(III) cations, the hydroxide (OH−
) anion, and another anion such as carbonate (CO2−
3), chloride (Cl−
), or sulfate (SO2−
4), in a layered double hydroxide (LDH) structure. The most studied varieties are the following:
Langbeinites are a family of crystalline substances based on the structure of langbeinite with general formula M2M'2(SO4)3, where M is a large univalent cation, and M' is a small divalent cation. The sulfate group, SO2−4, can be substituted by other tetrahedral anions with a double negative charge such as tetrafluoroberyllate, selenate, chromate, molybdate, or tungstates. Although monofluorophosphates are predicted, they have not been described. By redistributing charges other anions with the same shape such as phosphate also form langbeinite structures. In these the M' atom must have a greater charge to balance the extra three negative charges.
Iron(II) selenate (ferrous selenate) is an inorganic compound with the formula FeSeO4. It has anhydrous and several hydrate forms. The pentahydrate has the structure, [Fe(H2O)4]SeO4•H2O, isomorphous to the corresponding iron(II) sulfate. Heptahydrate is also known, in form of unstable green crystalline solid.
Vanadium(II) sulfate describes a family of inorganic compounds with the formula VSO4(H2O)x where 0 ≤ x ≤ 7. The hexahydrate is most commonly encountered. It is a violet solid that dissolves in water to give air-sensitive solutions of the aquo complex. The salt is isomorphous with [Mg(H2O)6]SO4. Compared to the V–O bond length of 191 pm in [V(H2O)6]3+, the V–O distance is 212 pm in the [V(H2O)6]SO4. This nearly 10% elongation reflects the effect of the lower charge, hence weakened electrostatic attraction.
Iron(II) perchlorate is the inorganic compound with the formula Fe(ClO4)2·6H2O. A green, water-soluble solid, it is produced by the reaction of iron metal with dilute perchloric acid followed by evaporation of the solution:
