Ferric hydroxide, 6.18

Very finely divided minerals may be difficult to purify by flotation since the particles may a ere to larger, undesired minerals—or vice versa, the fines may be an impurity to be removed. The latter is the case with Ii02 (anatase) impurity in kaolin clay [87]. In carrier flotation, a coarser, separable mineral is added that will selectively pick up the fines [88,89]. The added mineral may be in the form of a floe (ferric hydroxide), and the process is called adsorbing colloid flotation [90]. The fines may be aggregated to reduce their loss, as in the addition of oil to agglomerate coal fines [91]. 

Dissolve a small portion of the sodium derivative in a few mi. of water in a test-tube, and add one drop of ferric chloride solution. A deep red coloration is produced, but rapidly disappears as the iron is precipitated as ferric hydroxide. The sodium (derivative (A) of the nitromethane wh dissolved in water undergoes partial hydrolysis,... 

Ferric chloride solution is then added to com ert the sodium ferrocyanide to the deep blue ferric ferrocyanide (or Prussian Blue), dilute sulphuric acid being also added to dissolve any ferrous and ferric hydroxides present in the other-... 

Ferric chloride solution sometimes contains a large excess of HCl which would interfere with the following reactions. If it is very markedly acidic add dil. NaOH solution, drop by drop, to the ferric chloride solution until a small but permanent precipitate of ferric hydroxide is obtained. Filter this off through a small fluted filter paper, and use the clear filtrate. The latter is still not quite neutral owing to hydrolysis, but this feeble acidity does not interfere with the tests given below. 

Unless all the excess of ammonia has been driven off in the preparation of the neutral salt, the result obtained on adding ferric chloride will be misleading owing to the precipitation of ferric hydroxide. If this is suspected, the tests should be repeated using an aqueous solution of the pure sodium salts of these acids for comparison. 

Ferric chloride reaction. For the success of this reaction it is important that the solution should be neutral. Excess of acid usually inhibits the production of colour or precipitate, and excess of alkali gives a reddish-brown precipitate of ferric hydroxide. A neutral solution may be made as follows ... 

Upon boiling the alkaline ferrous salt solution, some ferric ions are inevitably produced by the action of the air upon the addition of dilute siilphurio acid, thus dissolving the ferrous and ferric hydroxides, the ferrocyanides reacts with the ferric salt producing ferric ferrocyanide (Prussian blue) ... 

Prepare the neutral ferric chloride solution (i.e., free from hydrochloric acid) by adding dilute sodium hydroxide solution dropwise to the bench reagent until a slight precipitate of ferric hydroxide is formed. Filter off the precipitate and use the clear filtrate for the test. 

Iron compounds (qv) in limestone are seldom injurious to a lime product unless a very pure lime is required. Normally, the iron compounds are in the form of limonite [1317-63-1] (ferric hydroxide) and pyrite [1309-36-0] EeS2. Occasionally, hematite, magnetite, marcasite, and other forms of iron are found in limestone. 

The ferrous hydroxide may react to form ferric hydroxide ... 

Metals and Metallic Ions. Under appropriate conditions, ozone oxidizes most metals with the exception of gold and the platinum group. When oxidized by ozone, heavy metal ions, such as Fe and Mn , result in the precipitation of insoluble hydroxides or oxides upon hydrolysis (48—50). Excess ozone oxidizes ferric hydroxide in alkaline media to ferrate, and Mn02 to MnO. ... 

Water. Based on the overall balanced equation for this reaction, a minimum of one mole of water per mole of nitro compound is required for the reduction to take place. In practice, however, 4 to 5 moles of water per mole of nitro compound are used to ensure that enough water is present to convert all of the iron to the intermediate ferrous and ferric hydroxides. In some cases, much larger amounts of water are used to dissolve the amino compound and help separate it from the iron oxide sludge after the reaction is complete. 

The ferrous hydroxide then combines with oxygen and water to produce ferric hydroxide, Fe(OH)2, which becomes common iron mst when dehydrated to Fe202. 

Petroleum. Citric acid is added to hydrochloric acid solutions in acidising limestone formations. Citric acid prevents the formation of ferric hydroxide gel in the spent acid solution by chelating the ferric ions present. Formation of the gel would plug the pores, preventing the flow of oil to the producer well (123—127). 

Ferric ammonium citrate [1185-57-5]—A mixture of complex chelates prepared by the iateraction of ferric hydroxide with citric acid ia the presence of ammonia. The chelates occur ia brown and green forms, are dehquescent ia air, and are reducible by light. 

Outer crust. A friable outer crust forms atop the tubercle. The crust is composed of ferric hydroxide (hematite), carbonates, silicates, other precipitates, settled particulate, and detritus. Ferrous ion and ferrous hydroxide generated within the tubercle diffuse outward through fis-... 

Multiple magnetite shells may form by successive fracture. Ferrous species spew out of the fractured shell and are quickly oxidized to form a new ferric hydroxide crust. Beneath the new crust, another mag-... 

The ferrous hydroxide is rapidly oxidized to ferric hydroxide in oxygenated waters (Reaction 5.5) ... 

Ferric and ferrous hydroxide usually contain water of hydration. A layer of hydrated magnetite sometimes forms between the ferric and ferrous hydroxides (see Fig. 3.2). The threefold layer of corrosion products is usually called rust. The bulk of rust is the ferric hydroxide layer. (In tubercles, however, ferrous hydroxide often is the major component see Chap. 3.)... 

Metal depositors. Metal-depositing bacteria oxidize ferrous iron (Fe ) to ferric iron (Fe ). Ferric hydroxide is the result. Some bacteria oxidize manganese and other metals. Gallionella bacteria, in particular, have been associated with the accumulation of iron oxides in tubercles. In fact, up to 90% of the dry weight of the cell mass can be iron hydroxide. These bacteria appear filamentous. The oxide accumulates along very fine tails or excretion stalks generated by these organisms. 

Feed solutions are usually made up at a water to chemical ratio of 2 1 to 8 1 (on a weight basis) with the usual ratio being 4 1 with a 20-minute detention time. Care must be taken not to dilute ferric sulfate solutions to less than 1 percent to prevent hydrolysis and deposition of ferric hydroxide. Ferric sulfate is actively corrosive in solution, and dissolving and transporting equipment should be fabricated of type 316 stainless steel, rubber, plastics, ceramics, or lead. 

Eisen-hydrozyd, n. ferric hydroxide, iron(III) hydroxide, -hydroxydul, n. ferrous hydroxide, iron(II) hydroxide. -jodid,n. iron iodide, specif, ferric iodide, iron(III) iodide, -jodiir, n. ferrous iodide, iron(II) iodide, -jodiirjo-did, n. ferrosoferric iodide, iron(II,IIl) iodide, kalium, n. potassium ferrate, -kaliumalaun,... 

As described in U,S. Patent 2,575,611, 107 parts of freshly prepared ferric hydroxide are added to 295 parts of choline dihydrogen citrate dissolved in 200 parts of distilled water and heated to approximately 80°C until a homogeneous solution occurs. The resulting reddish brown solution may be used as such or it may be dried by evaporating the water,... 

---