Ferrous chloride, oxidation

Iron oxide yellows can also be produced by the direct hydrolysis of various ferric solutions with alkahes such as NaOH, Ca(OH)2, and NH. To make this process economical, ferric solutions are prepared by the oxidation of ferrous salts, eg, ferrous chloride and sulfate, that are available as waste from metallurgical operations. The produced precipitate is washed, separated by sedimentation, and dried at about 120°C. Pigments prepared by this method have lower coverage, and because of their high surface area have a high oil absorption. 

Several modifications to this process are possible (55). Instead of adding ferrous chloride directiy, it is more common to generate it by using iron and hydrochloric acid. The order in which the reactants are added can also be altered, and it is even possible to add all of the iron or aniline at the beginning of the reaction. There are also other ways to recover the aniline from the iron oxide sludge. 

Flydrochloric acid regeneration. This process is used to treat the spent pickle liquor containing free hydrochloric acid, ferrous chloride, and water that is obtained from steel finishing operations. The liquor is concentrated by heating to remove some of the water, followed by thermal decomposition in a roaster at temperatures (925 to 1050°C) sufficient for complete evaporation of water and decomposition of ferrous chloride into iron oxide (ferric oxide, Fe203) and hydrogen chloride (HC1) gas.19 The iron oxide is separated for offsite recovery or... 

When iron oxides dissolve in hydrochloric acid, ferrous chloride is formed according to the following reactions ... 

The need for reducing agents is much less than for oxidizing agents. The most common agents are ferrous chloride or sulfate, sodium metabisulfite, hydrogen sulfide, and sulfur dioxide.35... 

Schnepfe [83] has described yet another procedure for the determination of iodate and total iodine in seawater. To determine total iodine 1 ml of 1% aqueous sulfamic acid is added to 10 ml seawater which, if necessary, is filtered and then adjusted to a pH of less than 2.0. After 15 min, 1 ml sodium hydroxide (0.1 M) and 0.5 ml potassium permanganate (0.1M) are added and the mixture heated on a steam bath for one hour. The cooled solution is filtered and the residue washed. The filtrate and washings are diluted to 16 ml and 1ml of a phosphate solution (0.25 M) added (containing 0.3 xg iodine as iodate per ml) at 0 °C. Then 0.7 ml ferrous chloride (0.1 M) in 0.2% v/v sulfuric acid, 5 ml aqueous sulfuric acid (10%) - phosphoric acid (1 1) are added at 0 °C followed by 2 ml starch-cadmium iodide reagent. The solution is diluted to 25 ml and after 10-15 min the extinction of the starch-iodine complex is measured in a -5 cm cell. To determine iodate the same procedure is followed as is described previously except that the oxidation stage with sodium hydroxide - potassium permanganate is omitted and only 0.2 ml ferrous chloride solution is added. A potassium iodate standard was used in both methods. 

EARS [Enhanced acid regeneration system] A process for recovering hydrochloric acid from the ERMS ilmenite beneficiation process. It may be used also for recovering waste pickle liquor. The acid liquor containing ferrous chloride is evaporated at low temperature to form iron chloride pellets, which are fed to a pyrohydrolysis reactor. This generates hydrochloric acid and iron oxide pellets, which can be used for steel production or disposed of as inert landfill. Developed by E. A. Walpole at the University of Newcastle, Australia, from the early 1990s and piloted by Austpac Gold (now Austpac Resources). 

Numerous methods for the synthesis of salicyl alcohol exist. These involve the reduction of salicylaldehyde or of salicylic acid and its derivatives. The alcohol can be prepared in almost theoretical yield by the reduction of salicylaldehyde with sodium amalgam, sodium borohydride, or lithium aluminum hydride by catalytic hydrogenation over platinum black or Raney nickel or by hydrogenation over platinum and ferrous chloride in alcohol. The electrolytic reduction of salicylaldehyde in sodium bicarbonate solution at a mercury cathode with carbon dioxide passed into the mixture also yields saligenin. It is formed by the electrolytic reduction at lead electrodes of salicylic acids in aqueous alcoholic solution or sodium salicylate in the presence of boric acid and sodium sulfate. Salicylamide in aqueous alcohol solution acidified with acetic acid is reduced to salicyl alcohol by sodium amalgam in 63% yield. Salicyl alcohol forms along with -hydroxybenzyl alcohol by the action of formaldehyde on phenol in the presence of sodium hydroxide or calcium oxide. High yields of salicyl alcohol from phenol and formaldehyde in the presence of a molar equivalent of ether additives have been reported (60). Phenyl metaborate prepared from phenol and boric acid yields salicyl alcohol after treatment with formaldehyde and hydrolysis (61). 

The logical way to meet this situation is to wash the crystals with some liquid that will dissolve the film and leave them clean and bright. Evidently, ferrous chloride will have to be soluble in this liquid, but its solubility should be rather small, so that the solution left upon the crystals will not be viscous and will dry rapidly. An alternative plan is to dilute the original solution with a solvent that will diminish the solubility of ferrous chloride and thus avoid some of the difficulties. Alcohol will serve this latter purpose, but it increases the solubility of oxygen in the solution, and this promotes oxidation. A better liquid is concentrated hydrochloric acid. This suggests the following procedure ... 

To prevent recomplexation of EDTA, a reducing agent such as ferrous sulfate or ferrous chloride is added in the first vessel at the low pH. A reduction-oxidation reaction takes place between ferrous ion and the metal and the free metal ions are reduced to their lowest balance state where they are least likely to recomplex. The ferrous ion is oxidized to ferric ion which, in turn, forms a ferric-EDTA complex of low toxicity.5... 

Under the most favourable conditions the highest percentage of ferric iron obtained is 8-8. The degree of oxidation is independent of the initial concentration of total iron. It has also been shown that oxidation by sulphur dioxide at 95° C. does not occur in solutions of ferrous chloride unless there are present at least 165 grams of free HC1 per litre. 

According to T. Curtius, feme chloride is reduced by hydrazine to ferrous chloride a reaction investigated by E. Miiller and G. Wegdin, and F. Schrader. E. J. Cuy found that in the reaction between hydrazine and a ferric salt in acid soln., one mol of hydrazine requires between one and two eq. of ferric salt for oxidation. The limiting reaction may be expressed as follows N2H 5-)-Fe" =NH 4+JN2+H +Fe". A. W. Browne and F. F. Shetterly showed that ferric oxide and hydrazine in aq. soln, yield ammonia, but no hydrazoic acid, while nickel sesquioxide and cobalt sesquioxide yield ammonia and traces of hydrazoic acid. H. Franzen and 0. von Mayer made complex cobalt salts—e.g. CoC12(N2H4)2, etc.—with hydrazine in place of ammonia. T. Curtius found that platinum is precipitated when a soln. of hydrazine is added to a neutral soln. of platinum... 

V. Kohlschiitter and M. Kutscheroff found that v litres of water containing a mol of ferrous chloride absorb S litres of nitric oxide thus ... 

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