Colloidal ferric hydroxid

Uranium coprecipitated with aluminium phosphate, precipitate dissolved in nitric acid Adsorption onto colloidal ferric hydroxide... 

To the filtered seawater (500 ml about 1.5 xg U) is added 0.05 M ferric chloride (3 ml), the pH is adjusted to 6.7 0.1 and the uranium present as (U02(C03)3)4- is adsorbed on the colloidal ferric hydroxide which is floated to the surface as a stable froth by the addition of 0.05% ethanolic sodium dodecyl sulfate (2 ml) with an air-flow (about 10 ml min-1) through the mixture for 5 min. The froth is removed and dissolved in 12 M hydrochloric acid-16 M nitric acid (4 1) and the uranium is salted out with a solution of calcium nitrate containing EDTA, and determined spectrophotometrically at 555 nm by a modification of a Rhodamine B method. The average recovery of uranium is 82% co-adsorbed WO4- and M0O4- do not interfere. 

Fox, L.F. (1988) The solubility of colloidal ferric hydroxide and its relevance to iron concentrations in river water. Geochim. Cosmochim. Acta 52 771-777... 

When water pH is <6, iron corrosion and the formation of corrosion products such as colloidal ferric hydroxide can result. Colloidal ferric hydroxide, however, is difficult to detect and difficult to remove through filtration. Fuel containing these particles appears bright and clear. Only about 1 micron in diameter, colloidal ferric hydroxide compounds can pass through fuel filters and deposit onto fuel system components. Further system corrosion can follow. 

Ferrous hydroxide can continue to react with water and oxygen to form colloidal ferric hydroxide ... 

Decarlo, E. H. Thomas, D. M. 1985. Removal of arsenic from geothermal fluids by adsorptive bubble flotation with colloidal ferric hydroxide. Environmental Science Technology, 19, 538-544. 

Excessively dilute solutions of ferric chloride9 give no coloration with potassium ferrocyanide, the salt being completely hydrolysed and converted into colloidal ferric hydroxide (see p. 125). 

Colloidal ferric hydroxide.—Ferric hydroxide may be obtained in colloidal solution10 by adding 5 c.c. of 33 per cent, ferric chloride to a litre of boiling water and removing the chloride remaining, together with the hydrochloric acid, by dialysis. 

Another method consists in boiling a solution of ferric nitrate with copper filings or zinc dust. The ferric nitrate need not be specially isolated for the purpose, but may be made merely as an intermediate product during the course of the reaction—if, for example, iron filings containing copper are treated with concentrated nitric acid. After dilution and filtration, the solution is dialysed, whereby a deep red liquid is obtained, containing colloidal ferric hydroxide.1... 

When a 10 per cent, solution of ferric chloride is poured into excess of ammonia, the colloidal ferric hydroxide initially produced is coagulated by the ammonium chloride. On evaporating to dryness and washing with water, the ammonium salt washes out, and then the ferric hydroxide deflocculates, passing into subsequent wash waters as a red colloidal solution.4... 

The colloid, as usually prepared, is electro-positive in character, and may be precipitated from solution by electrolysis, by the addition of small quantities of electrolytes, or by the action of an oppositely charged colloid, such, for example, as (negative) arsemous sulphide, whereby the two electrical charges neutralise each other.7 The smallest quantities of a few electrolytes required to precipitate colloidal ferric hydroxide from solution are given in the following table —8... 

It is possible also to prepare colloidal ferric hydroxide with a negative charge. This may be done by adding slowly 100 c.c. of 0 01-normal ferric chloride solution to 150 c.c. of 0-01-normal sodium hydroxide, the mixture being continuously shaken during the process.2... 

Negative colloidal ferric hydroxide may be converted into the positive colloid by adding it to a very dilute solution of sodium hydroxide (0 005-normal) with constant shaking. In order to account for this amphi-electrical behaviour, it is suggested that the potential difference at the surface of colloidal particles is due to adsorption of ions from the solution. Hence the sign depends upon whether cations or anions are in excess in the layers nearest the particles.5... 

Attempts to determine the molecular weight of colloidal ferric hydroxide lead to very high values. Thus, a colloidal solution prepared by addition of ammonium carbonate to ferric chloride solution was purified by dialysis, and the freezing-point determined of that portion which would not pass through a collodion membrane. The point was only slightly lower than that of the filtrate, indicative of a molecular weight of 3120 for the colloid.2... 

For particulars of further researches on colloidal ferric hydroxide the reader is referred to the subjoined references.6... 

The heat of coagulation of colloidal ferric hydroxide with potassium oxalate has been studied by Doerinckel.7... 

A study of the electric conductivities of aqueous solutions of the salt indicates that the hydrolysis proceeds in two stages, embodying (1) a rapid change unaccompanied by precipitation, and (2) a slower change, progressing at a measurable rate, and accompanied by the production of a so-called basic salt.8 Colloidal ferric hydroxide does not appear to be formed during hydrolysis,9 the salt thus differing from ferric chloride and nitrate. 

In dilute solution ferric nitrate is hydrolysed, yielding colloidal ferric hydroxide and free nitric acid. Such solution gives no coloration with potassium ferrocyanide. In less dilute solutions, to which potassium ferrocyanide has already been added, the blue colour gradually intensifies owing to the continued re-formation of ferric nitrate, as the equilibrium represented by the equation... 

In very dilute solution the intensity of colour produced is not quite proportional to the amount of iron present—indeed, the more concentrated solution becomes decolorised on dilution, as also by addition of oxalates, tartrates, etc. The decoloration on dilution is usually explained on the assumption that the water hydrolyses the red undissociated salt into yellow colloidal ferric hydroxide and free thio-cyanic acid —... 

Iron and Oxygen—Ferrous Oxide and Hydroxide—Magnetic Oxide—Ferric Oxide—Polymorphism—Hydrated Ferric Oxide—Ferrous Acid—Colloidal Ferric Hydroxide—Ferrites—Ferrates—Perferrates. 

The origin of the surface charges, and of the double layers is probably different for different materials. Thus colloidal ferric hydroxide... 

E.A.C. Follett, W. J. McHardy, B. D. Mitchell, and B.F.L. Smith, Chemical dissolution techniques in the study of soil clays. Clay Minerals 6 23 (1965). E.A.C. Follett, The retention of amorphous, colloidal ferric hydroxide by kaolinites, J. Soil Sci. 16 334 (1965). A. W. Fordham and K. Norrish, Electron microprobe and electron microscope studies of soil clay particles, Aust. J. Soil Res. 17 283 (1979). 

The resulting colloidal ferric hydroxide particles are amorphous and grow to average particle diameters of 3-5 nm [35,36]. It is estimated that a typical primary particle ( 3.8 nm diameter) contains 820 Fe atoms [35]. Crystalline phases such as goethite (as-FeOOH) and akagemite ( FeOOH) develop from this initial material when the spherical amorphous colloidal particles link up to form rods, and the rods in turn aggregate to form rafts [35,36]. 

A solution of ferritin mixed with sodium hydroxide gives rise to a brown precipitate of ferric hydroxide, which is not precisely of the composition FeOOH, but contains some phosphate, just as all amorphous ferric hydroxides, especially those obtained from coagulation of any colloidal ferric hydroxide sol, contains some anionic constituents other than OH. The phosphorus content of that precipitate is smaller than would correspond to the ratio 1 9 mentioned above. A part of the phosphate seems to be split off from its attachment to iron, when the iron is precipitated by sodium hydroxide. 

The constancy and reproducibility of the magnetic susceptilnlity of the iron atom in ferritin is even more remarkable as the susceptibility of artificially prepared colloidal ferric hydroxide was found to be very variable, according to the method of its preparation. Although it is... 

The peptisation of most oxides, sulfides and salts may be explained on the same basis.- According to Graham the peptisation of ferric hydroxide hydrogel takes place on treating it with ferric chloride. One may assume that the ferric ion attaches itself to the ultramicrons of the colloidal ferric hydroxide, thus imparting to the latter the positive charge. 

Between these two extremes, liquid particles suspended in a medium, on the one hand, and solid particles on the other, all possible grades exist. For instance colloidal ferric hydroxide, highly dispersed, has many properties of liquids in a similar condition. When it is coagulated, however, the resulting flocks cannot be considered a pure liquid. In fact it is better to call this and other solids not having a crystalline structure, supercooled liquids. 

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