Ferrous iodate

A. Connell (1802) 140 obtained a white precipitate—ferrous iodate—by boiling a soln. of iron in iodic acid, and C. F. Rammelsberg found that the addition of potassium iodate to ferrous sulphate gives a yellowish-white precipitate which is decomposed when heated. It is sparingly soluble in nitric acid, and it dissolves in an excess of ferrous sulphate, and the soln., when heated, precipitates basic ferric iodate. A. Ditte mixed boiling soln. of a ferric salt and an alkali iodate and obtained a brown precipitate—ferric iodate—insoluble in hot nitric acid diluted with its own volume of water. Crystals can be obtained by mixing warm dil. soln. of ferric nitrate, acidified with nitric acid, and sodium iodate. The precipitate... 

Ferrous iodate.—On addition of potassium iodate to ferrous sulphate solution, a pale yellow precipitate is obtained, consisting probably of ferrous iodate.4... 

Ferrous Sulfdte Titration. For deterrnination of nitric acid in mixed acid or for nitrates that are free from interferences, ferrous sulfate titration, the nitrometer method, and Devarda s method give excellent results. The deterrnination of nitric acid and nitrates in mixed acid is based on the oxidation of ferrous sulfate [7720-78-7] by nitric acid and may be subject to interference by other materials that reduce nitric acid or oxidize ferrous sulfate. Small amounts of sodium chloride, potassium bromide, or potassium iodide may be tolerated without serious interference, as can nitrous acid up to 50% of the total amount of nitric acid present. Strong oxidizing agents, eg, chlorates, iodates, and bromates, interfere by oxidizing the standardized ferrous sulfate. 

Bromide ndIodide. The spectrophotometric determination of trace bromide concentration is based on the bromide catalysis of iodine oxidation to iodate by permanganate in acidic solution. Iodide can also be measured spectrophotometricaHy by selective oxidation to iodine by potassium peroxymonosulfate (KHSO ). The iodine reacts with colorless leucocrystal violet to produce the highly colored leucocrystal violet dye. Greater than 200 mg/L of chloride interferes with the color development. Trace concentrations of iodide are determined by its abiUty to cataly2e ceric ion reduction by arsenous acid. The reduction reaction is stopped at a specific time by the addition of ferrous ammonium sulfate. The ferrous ion is oxidi2ed to ferric ion, which then reacts with thiocyanate to produce a deep red complex. 

Ammonium-ferrisulfat, n. ammonium iron(III). sulfate, ferric ammonium sulfate, -ferro-sulfat, n. ammonium iron(II) sulfate, ferrous ammonium sulfate, -jodat, n. ammonium iodate. -jodid, n. ammonium iodide, -platinchlorid, n. ammonium platinichloride (chloroplatinate). -rest, m. ammonium radical. rhodanid, -rhodantir, n. ammonium thiocyanate, -salpeter, m. ammonium nitrate, -salz, n. ammonium s t. -selfe,/. ammonia soap, -sulfhydrat, n. ammonium hydrosulfide, -sulfocyanid, n. ammonium thiocyanate, -verbindung,/. ammonium compound, -zinn-chlorid, n. ammonium chlorostannate, pink salt. 

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. 

Silver foil is transformed by an aq. soln. of the trichloride into silver chloride and iodide silver oxide with an excess of the trichloride is transformed into the chloride and iodic acid with more silver oxide, silver iodate is formed and with an excess of the oxide and a boiling soln. some silver periodate is formed. Mercuric oxide is slowly transformed into mercuric chloride and oxide chlorine, oxygen, and possibly chlorine monoxide are evolved. Aq. soln. of the trichloride give a precipitate of iodine with a little stannous chloride with more stannous chloride, some stannous iodide is formed. Consequently, although chloroform extracts no iodine from the aq. soln., it will do so after the addition of stannous chloride. Sulphur dioxide and ferrous sulphate are oxidized. 

Like the arsenite-iodate reaction, chlorite-iodide is a clock reaction50,51 however, it is more complex. This reaction shows a dramatic rise in the intensity of the brown color of iodine, followed by an even more abrupt fade-out. This behavior resembles that of the ferrous-nitrate clock, where the color is due to formation of the FeNOz+ complex52. ... 

Sodium iodide, Nal.—The iodide is prepared by neutralizing sodium hydroxide or earbonate with hydriodic acid or by the action of iodine on sodium hydroxide, and reduction with charcoal of the iodate simultaneously formed or from sodium hydroxide and iodine in presence of iron-filings or ferrous iodide. 

Two ferrous per-iodates are described by Kimmins,3namelyFe5(I06)2 and FeHs(I06). The former is a brick-red crystalline salt produced on adding ferrous sulphate to a solution of K4I209. FeH3(IOe) results as a light brown powder on adding a solution of Na2H3I06 to ferrous sulphate. 

Ferrous sulphate undergoes hydrolysis when its solution is boiled with potassium iodide and iodate. Thus —... 

The excess of iodate then oxidises the ferrous hydroxide to the ferric condition.4... 

The high solubility of potassium iodate enables dispersion into the solution quickly, and at the same time renders the salt comparatively less stable than iodate, especially in acidic pH. The salt also tends to disintegrate in the presence of moisture or with interaction with reducing salts such as ferrous and zinc sulfate in the formulation. 

It is easily perceived that the ferrous species is oxidized and the iodate is reduced. 

Dissolve a quantity of sample to contain about 0 25 g of ferrous iron in 20 ml of 25 per cent w/v sulphuric acid, add 6 ml of strong iodine monochloride solution and 60 ml of concentrated hydrochloric acid and titrate with 0 05M potassium iodate, using 5 ml of chloroform as indicator. 1 ml 0-05M potassium iodate = 0 01117 g Fe 0 02317 g FeCOa 0 03038 g FeS04. 

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