Ferric hydroxide, preparation colloidal

If ferric hydroxide be prepared by the hydrolysis of ferric chloride the resulting colloid contains chlorine ions which can be replaced by more readily adsorbable picrate or eosinate ions leaving hydrochloric acid in solution. 

One of the earliest known chemical properties of ferric salts was their ready conversion to ferric hydroxide colloids in solutions. These solutions were intensively studied in the classic period of colloid chemistry, and their properties have been discussed in detail by Weiser (8). Since the focus of these studies was on colloid properties per se, precautions were taken to prepare pure colloids. Generally hydrolyzed solutions would be dialyzed extensively against distilled water to remove foreign ions. Even the purest preparations retained detectable concentrations of anions, consistent with a positive surface charge on the colloidal particles. 

Colloidal saccharated iron is sometimes used in place of ferric hydroxide as an antidote in arsenical poisoning, but its adsorptive capacity depends on the alkalinity of the medium.4 Thus a commercial preparation containing 0-75 per cent, of sodium hydroxide was found to adsorb 12-57 per cent, of arsenious oxide (reckoned on the amount of iron present) addition of alkali increased the adsorption until, with 1-28 per cent, of sodium hydroxide present, there was a maximum adsorption of 27 per cent. The addition of acid correspondingly diminished the adsorption. A gel of ferric magnesium hydroxide, if prepared without boiling, also adsorbs arsenic from sodium arsenite solutions.5... 

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)... 

Ferric hydroxide sol A colloidal solution of ferric hydroxide is obtained by adding a freshly prepared saturated solution of ferric chloride (2 or 3 ml) drop by drop to 500 ml of boiling distilled water. Ferric chloride hydrolyses to give a brown sol of ferric hydroxide sol. 

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... 

Ferric hydroxide is not unique in this respect, for stannic hydroxide has likewise been prepared both as a positive3 and a negative 4 colloid. 

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 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 colloidal phosphate, prepared by the action of concentrated ammonium hydroxide on ferric phosphate, has been studied by Holmes and Rmdfusz, J. Amer. Chem. Soc., 1916, 38, 1970. 

Colloidal ferric arsenate is prepared by the action of ammonium hydroxide on the insoluble salt.10... 

The common method for preparing a colloidal solution of hydrous ferric oxide, for example, has been to hydrolyze ferric chloride in solution by heat, and remove the hydrochloric acid by dialysis. Colloidal silica can be made in a similar way, that is, by dialyzing a solution of sodium silicate. One hydrolysis product—hydrochloric acid or sodium hydroxide—can pass through the membrane used for dialysis, whereas the colloidal particles of hydrous oxide cannot. The process is rather tedious and takes hours or even days. A much simpler method is to take out the acid or alkali with one of the solid ion exchangers or acid absorbers used in water purification. ... 

Materials. Colloid Particles. The ferric hydrous oxide sol was prepared by acid hydrolysis of 0.019 M FeCla solutions containing 10 M HCl over a period of three weeks at room temperature. This yielded the p form of the oxide-hydroxide (7-8), Free Fe ions were removed by repeated centrifugation. In some instances, dialysis of the sol against deionized water was also done to obtain the sol free of Fe " " ions. The structure of jSFeOOH is of hollandite type. The method of preparation gives ellipsoidal shaped particles uniform in shape and of narrow size distribution - Figure 1. The morphology was studied extensively and needs... 

George A., Wilson W.W. Predicting protein crystallization from a dilute solution property. Acta Crystallogr. Sect. D Biol. Crystallogr. 1994 50 361-365 Grant M.C., Russel W.B. Volume-fraction dependence of elastic-moduli and transition— Temperatures for colloidal silica-gels. Phys. Rev. E 1993 47(4) 2606-2614 Hamada S., Matijevic E. Eerric hydroxide sols FV. Preparation of uniform cubic hematitie particles by hydrolysis of ferric chloride in alcohol-water solutions. J. Colloid Interface Sci. 1981 84(1) 274-277... 

The starting materials were soluble salts, cobalt acetate (Co(C2H302)2 H2O) and iron nitrate (Fe(N03)2 9H2O). These salts produce hydroxides (M(OH)2), oxyhydroxides (MOOH) or hydrated oxides in water, where M is Co or Fe. These solutions were reacted with lithium hydroxide. Diluted ammonium hydroxide (3M) was added to form stable colloids (Barboux, 1991). Lithium hydroxide and cobalt acetate were dissolved separately in distilled water. These two solutions were then mixed together and stirred vigorously. The hydrolysis of the mixture was promoted by slow addition of 3M ammonium hydroxide. Similarly, sols with ferric nitrate, or ferric nitrate plus cobalt acetate, were prepared. The sols used for coating were diluted to give a 2 1 ratio of moles water to moles oxide. 

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