25. colloidal ferric carbonate

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... 

The fact that Prussian blue is indeed ferric ferrocyanide (Fe4in[Fen(CN)6]3) with iron(III) atom coordinated to nitrogen and iron(II) atom coordinated to carbon has been established by spectroscopic investigations [4], Prussian blue can be synthesized chemically by the mixing of ferric (ferrous) and hexacyanoferrate ions with different oxidation state of iron atoms either Fe3+ + [Fen(CN)6]4 or Fe2+ + [Fem(CN)6]3. After mixing, an immediate formation of the dark blue colloid is observed. However, the mixed solutions of ferric (ferrous) and hexacyanoferrate ions with the same oxidation state of iron atoms are apparently stable. 

Amhamdi, FI. Dumont, F. Buez-FIerman, C. (1997) Effect of urea on the stability of ferric oxide hydrosols. Colloids Surfaces 125 1-3 Amin, N. Arajs, S. (1987) Morin temperature of annealed submicronic a-Fe20j particles. Phys. Rev. B35 4810-4811 Amonette, J.E. Workman, D.J. Kennedy, D.W Fruchter, J.S. Gorby Y.A. (2000) Dechlorination of carbon tetrachloride by Fe(II) associated with goethite. Environ. Sci. Techn. 34 4606-4613... 

P roblem 3 How will you prepare the colloidal solutions of the following Arsenic sulphide, ferric hydroxide, gold, sulphur, silicic acid, carbon, iodine, mastic. (Meerut 2000)... 

By saturating a solution of ferric chloride with ammonium carbonate and purifying the solution thus obtained by dialysis, ferric hydroxide is readily obtained in the colloidal state,2 or by dialysing the solution obtained by adding ammonia to a solution of ferric chloride in such small quantities at a time that the ferric hydroxide at first thrown out is completely dissolved on stirring. The clear, dark brown solution so obtained scarcely tastes of iron. The last traces of chlorine are not removed in this way, although the colloid is free from ammonium salts.3... 

Interferences are expected from colloids (not retained by the 0.45 im filter), and various UV absorbing inorganics such as ferrous iron. When hematite colloids or ferric chloride coagulant were added to samples, the UV measurement did not give any information about carbon content, as the absorbance of hematite or ferric chloride was identical or higher than that of the organics. 

The calcium cation produces many relatively insoluble salts. The most insoluble is calcium oxalate. Oxalic acid is used to demonstrate the presence of calcium in a liquid as it causes turbidity and precipitation. Calcium tartrate is also relatively insoluble, especially in the presence of ethanol (Section 1.6.5). In the same way, calcium gluconate and mucate, present in wine made from botrytized grapes, are reputed to be responsible for crystalline turbidity (Section 1.2.2). Calcium concentrations in white wines are between 80 and 140 mg/1, while they are slightly lower in red wines. The calcium content may increase following deacidification with calcium carbonate. As calcium is divalent, it is more energetically involved than potassium in colloid flocculation and precipitation, e.g. ferric phosphate, tannin-gelatin complexes, etc. 

Beryllium is separated from aluminum and iron by the complete solubility of its hydroxide in a hot saturated solution of acid sodium carbonate—ferric hydroxide and aluminum hydroxide being completely insoluble. Double precipitation i.s essential. Beryllium hydroxide must lx washed with water containing an electrolyte in solution, for when i irc it rapidly washes through the filter in a colloidal condition. 

It is well known that nanoparticulate colloidal dispersions of PANI in various paints at low concentrations cause tremendous improvements in corrosion protection [504]. PANI-NFs showed similar anticorrosive effects e.g., carbon steel coated with PANI-NFs has better corrosion protection than that with aggregated PANI. Raman spectroscopy analysis indicated that the surface of carbon steel coated with PANI-NFs formed a better passive layer, which is composed of a-ferric oxide and Fc304 [146]. The corrosion resistance performance of soya oil alkyd containing nanostructured PANI composite coatings has recently been studied [447]. An array of Fe nano wires within PANI-NTs was obtained using a two-step template synthesis [316]. This PANI-NT envelope may protect the Fe nanowires against a corrosive atmosphere. 

In a study of the surface modification of poly(bisphenol A carbonate) by sul-fochromic acid, application of this approach to the Is/Ic intensity ratio led to a density of 4-10 sulphur atom cm, which was found unrealistic and lead to the conclusion that the polymer was attacked and that sulfate was incorporated over a certain depth. This pretreatment made the zeta potential of the material more negative. It increased the uptake of ferric hydroxide colloids in subsequent adsorption tests, which in turn made the zeta potential more positive. As a consequence the promotion of yeast cell adhesion by the ferric hydroxide treatment was less affected by drying. 

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