Iron compounds Potassium ferricyanide

Iron(III) acetylacetonate, 211 Iron carbonyl, 152 Potassium ferricyanide, 255 Tri-jji-carbonylhexacarbonyldiiron, 320 Lead Compounds Iodine-Lead tetraacetate, 243 Lead tetraacetate, 62, 95, 155, 295 Lead tetraacetate-Diphenyl disulfide, 156... 

Chemical properties of iron. Passivity. Ferrous compounds ferrous sulfate, ferrous ammonium sulfate, ferrous chloride, ferrous hydroxide, ferrous sulfide, ferrous carbonate. Ferric compounds ferric nitrate, ferric, sulfate, iron alum, ferric chloride, ferric hydroxide, ferric oxide (rouge, Venetian red). Potassium ferro-cyanide, potassium ferricyanide, Prussian blue. 

The iron salts of ferro and ferricyanic acid are the compounds to which the names cyanogen and cyanide are due. Two of these salts are of deep blue color and the Greek word from which cyanogen and cyanide are derived is cyanos which means blue. The ferric ferro-cyanide, Fe4 "(Fe"(CN6)3, is known as Prussian blue and the ferrous ferri-cyanide, Fe3"(Fe" (CN)6)2, is Turnbull s blue. These compounds are formed when ferric salts in solution are treated with potassium ferro-cyanide and when ferrous salts in solution are treated with potassium ferricyanide. They are common qualitative tests for the two forms of iron salts. The compounds are also used as laundry blueing and are formed in the blue print process of photography. 

Of a variety of metal compounds described in this section, iron compounds represented by ferric chloride (FeCF) and potassium ferricyanide [K3Fe(CN)6] have long been used for phenolic oxidation, particularly for biomimetic syntheses of benzylisoquinoline alkaloids and neolignans ° . ... 

K3Fe(CN), potassium ferricyanide) is an orange crystalline compound. Its solution gives a deep blue precipitate with iron(II) ions, and is used as a test for iron(II) (ferrous) compounds. Prassian blue is a blue pigment containing hexacyanoferrate ions. 

Since a main objective of the test is to differentiate between Fe + and Fe ", and since this is obtained by using Fe and Fe + reagents, it is important to recapitulate how these compoxmds are named. Iron in oxidation level two, Fe ", is called iron(ll), and its salts are called ferro compoxmds (e.g., potassium ferrocyanide) or ferrate(ll) compounds (hexacyanoferrate(ll)). Iron in oxidation level three, Fe , is called iron(lll), and its salts are called ferri compoxmds (e.g., potassium ferricyanide) or ferrate(lll) compoxmds (hexa-cyanoferrate(lll)). 

Both [(C5Me5)Fe(CO)2]2 "" and [(C5MeR4)Mn(CO)2(THF)] (R = react with tetracyanoethylene and tetracyanoquinodimethane to give the respective anions through electron transfer. Complexation of the iron fragment leads to a polymeric compound. When potassium ferricyanide is ground in a dry atmosphere, cyanogen and ferrocyanide are produced in amounts consistent with... 

A Figure 2.25 Compounds of ions of the same element but with different charge can be very different in appearance. Both substances shown are complex salts of iron with and CN ions. The one on the left is potassium ferrocyanide, which contains Fe(ll) bound to CN" ions. The one on the right is potassium ferricyanide, which contains Fe(lll) bound to CN ions. Both substances are used extensively in blueprinting and other dyeing processes. 

The differences between the individual iron-cyanide complex processes stem from the type of complex selected and the method of regeneration. In two processes, that of the Gesellschaft fur Kohlentechnik and the Fischer process, alkaline aqueous solutions of potassium ferricyanide and ferrocyanide are used, and regeneration is carried out by contact with air and electrolysis, respectively. The other two processes of this category, the Staatsmijnen-Otto and the Autopurification processes, employ suspensions of complexed ferric-ferro-cyanide compounds in alkaline solutions that are regenerated by air contact. The latter two processes are essentially identical, although they were developed independently in 1945 in the Netherlands and in England, respectively. 

If one pyrolyzes Prussian blue gently in a vacuum or. better, precipitates ferrous ferricyanide in the presence of a reducing agent such as potassium iodide or sucrose, the compound formed is truly iron(lI) hexacyanoferrateUlI).95 However, it reverts to Prussian blue rapidly upon warming with dilute hydrochloric add or standing in humid air. 

Other anomalous compounds are complex salts, e.g. potassium ferro-cyanide, K4Fe(CN)e, and ferricyanide, K3Fe(CN)e, which do not give the reactions of iron or cyanides, and potassium chloroplatinite, K2PtCl4, and chloroplatinate, KgPtCle, which do not answer the tests for platinum or chlorides. 

Iron can assume the oxidation states+2, +3, and +6, the last being rare, and represented by only a few compounds, such as potassium ferrate, KaFeOj. The oxidation states +2 and +3 correspond to the ferrous ion, Fe ", and ferric ion, Fe, respectively. The ferrous ion has six electrons in the incomplete 2>d subshell, and the ferric ion has five electrons in this subshell. The magnetic properties of the compounds of iron and other transition elements are due to the presence of a smaller number of electrons in the 3td subshell than required to fill this subshell. For example, ferric ion can have all five of its 2>d electrons with spins oriented in the same direction, because there are five 2>d orbitals in the 3d subshell, and the Pauli principle permits parallel orientation of the spins of electrons so long as there is only one electron per orbital. The ferrous ion. is easily oxidized to ferric ion by air or other oxidizing agents. Both bipositive and terpositive iron form complexes, such as the ferrocyanide ion, Fe(CN)e and the ferricyanide ion, Fe(CN)e, but they do not form complexes with ammonia. 

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