Iron chloride: neutral solution

If oxidising salts are present in neutral solutions they may reduce corrosion of the iron by the establishment of thin protective films on the metal surface. Their effectiveness is considerably diminished if much chloride ion is also present in solution. 

In 1813 Hatchett published in the Annals of Philosophy a method of separating iron and manganese (31). This paper was in the form of a letter to Thomas Thomson, the editor, and was dated Mount Clare, Roehampton, Sept. 25, 1813. A. F. Gehlen had used succinic acid to separate these two metals, Professor J. F. John had used oxalic add, but Hatchett simply precipitated the ferric hydroxide from a neutral solution containing ammonium chloride, leaving the manganese in solution. 

Iron (III) chloride Buff-colored precipitate of iron (III) benzoate from neutral solution soluble in hydrochloric acid... 

If a neutral solution of iron(III) chloride is added to a freshly prepared, saturated solution of hydrogen sulphide, a bluish colouration appears first, followed by the precipitation of sulphur. The blue colour is due to a colloid solution of sulphur of extremely small particle size. This reaction can be used to test the freshness of hydrogen sulphide solutions. 

The reactions of all these anions will be systematically studied in the following pages. For convenience the reactions of certain organic acids are grouped together these include acetates, formates, oxalates, tartrates, citrates, salicylates, benzoates, and succinates. It may be pointed out that acetates, formates, salicylates, benzoates, and succinates themselves form another group all give a characteristic colouration or precipitate upon the addition of iron(III) chloride solution to a practically neutral solution. 

Iron(III) chloride a red colouration, due to the complex [Fe3(HCOO)6]3+, is produced in practically neutral solutions the colour is discharged by hydrochloric acid. If the red solution is diluted and boiled, a brown precipitate of basic iron(III) formate is formed. 

Iron(III) chloride solution intense violet-red colouration with neutral solutions of salicylates or with free salicylic acid the colour disappears upon the addition of dilute mineral acids, but not of a little acetic acid. The presence of a large excess of many organic acids (acetic, tartaric, and citric) prevents the development of the colour but the addition of a few drops of dilute ammonia solution will cause it to appear. 

Iron (III) chloride solution light-brown precipitate of basic iron(III) succinate with a neutral solution some free succinic acid is simultaneously produced, and the solution becomes slightly acidic. 

Potassium hexacyanoferrate(III) andiron(III) chloride To a nearly neutral solution of iron(III) chloride add some potassium hexacyanoferrate(III) solution. A yellow solution is obtained. To this, add a nearly neutral solution of hydrogen peroxide. The solution turns to green and Prussian blue separates slowly. 

Test with iron(III) chloride solution Treat the other portion of the neutral solution from test 5 with aqueous iron(III) chloride solution. 

Sodium ferrifluoride, Na3FeF6, is obtained on adding ferric chloride or fluoride to a neutral solution of sodium fluoride.5 It is formed as a white, crystalline precipitate, which is only sparingly soluble in water. It does not give a red colour with thiocyanates, thus indicating that the iron atom is part of the negative radicle.6... 

It was observed for chloride-breakdown of the passive film on metallic iron in neutral borate solution that the amount of chloride ions required for initiating the local passivity breakdown is dependent on the film thickness, film defects, and electric field in the film as well as on the solution pH [41,42]. It was also observed that at the initial stage of the passivity breakdown the passive film locally dissolves and becomes thinner around the breakdown embryo before the underlying metal begins to dissolve in pitting at the passivity breakdown site [42,43]. From these observations, it is likely that the passivity breakdown is not a mechanical rupture of the passive film but a localized mode of dissolution of the passive film accelerated by the adsorption of aggressive anions on the film. 

The neutralized Nafion samples have been obtained by soaking the acid samples in solutions containing iron chloride or sodium hydroxide. 

Styptic Paper. A mode for carrying about chloride of iron as a ready styptic has been invented in Paris, which consists in dipping paper in a decoction of I pound ben2oin ana 1 pound alum in 4 gallons water, which has been kept boiling for 4 hours, with renewal and Bkimtning. Hie paper is left in the filtered solulion for somo timo until saturated it is then dried, and painted over with a neutral solution of percbloride of iron this is then dried, folded, and wrapped in an impervious cover. 

When moist hydrated peroxide of iron is mixed with a neutral solution of protochloride of tin, an exchange takes place, and a bulky precipitate of a grey colour is formed, which is a hydrate of sesquioxide of tin. Fe Oj -p 2 SnCl = Sn, 0,-1-2 FeCl. The sesquioxide is soluble in acids and in ammonia, the latter character distinguishing it from the protoxide. Its solution in hydrochloric add forms, with chloride of gold, the purple of Cassius and seems, indeed, better adapted for making it than the protoxide. 

Figure 4.1. Conditions of quasi-plug-flow mode (1-4) and torch front (5, 6) formation under proceeding of following reactions neutralization (1) interaction of potassium thiocyanate with iron chloride in acid (2) and neutral (3, 5) mediums mixing of methyl green solution with water (4, 6). (di / dd = 0,44, see 2.2.5)...

Interfering S032 can be eliminated by H2O2 in neutral solution, and 5203 , CN and SCN can be eliminated by H2O2 in alkaline solution. Iron ions can be precipitated by shaking with 1 g of chloride-free zinc oxide and can then be filtered off. Phosphate interferes in concentrations greater than 25 mg/1. It is coprecipitated with iron. 

Chloride ion accelerates the corrosion of iron in acidic solutions. The role of other halides is less clear and iodides and perhaps bromides may even serve as corrosion inhibitors. At near neutral pH values chloride has less effect than dissolved oxygen [27]. 

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