Potassium iron alum

Potassium-Iron Alum (Fetric Potassium Sulfate or Iron Alum), KaS04. Fea(S04)3 24HaO, mw 1006.5, mp 33°, d 1.806. Prepd by mixing equi molecular amts of ferric and... 

As a preliminary, ferric sulfate is made by the oxidation of ferrous sulfate. Dissolve 100 g. of ferrous sulfate in 100 cc. of boiling water, to which has been added before heating 10 cc. of sulfuric acid. Add concentrated nitric acid portionwise to the hot solution, until a diluted sample gives a reddish-brown (not black) precipitate with ammonia. This will require about 25 cc. Boil the solution down to a viscous liquid to get rid of excess nitric acid, dilute to about 400 cc., and add the calculated weight of ammonium sulfate. The crystallization is conducted as in the former exercise, preferably under 20°. By the addition of potassium sulfate, the corresponding potassium iron alum may be secured. In this case, it is necessary to concentrate the solution until there is about four parts of water to one of the hydrated alum and cool to about zero to secure crystallization. Both of these alums are amethyst in color, the potassium salt being much less stable and having a rather low transition point. 

Cond Chem Dict( 1956),279 Potassium-Iron Alum (Ferric Potassium Sulfate or Iron Alum), K2S04. Fe2(S04)j7 24H20, mw 1006.5, mp 33°, d 1.806. Prepd by mixing equi molecular amts of ferric and K sulfate and cor.eg the soln spontaneously. It forms fine violet octahedra crysts, liable to decomp to a brown deliquescent mass. Iron alum is sol in w, insol in ale. This... 

Potassium Hydrogen Acetylide A79-L Potassium-Iron Alum A156-R Potassium-5-nitraminotetrazoIe A260-L... 

Dipotaasie diferrio tefcnundphate. (Potassium iron alum.) Fig. 8. 

Eisen-alaun, m. iron alum (ferric potassium sulfate), -amiant, m. (Iron) fibrous silica.. ammonaiauQ, m. ammonium ferric alum.. ammonaiaunldsuQg, /. solution of ammonium iron salt, esp. ammonium ferric alum. -antimonerZ) n., -antimonglanz, m. berthier-ite. 

This solution is then diluted and titrated with standard potassium thiocyanate solution, using ammonium iron alum as indicator.1... 

A solution of iron alum, containing about 14 gms. per litre, and acidified with sulphuric acid until the solution assumes a pale straw colour, is prepared. By titrating 25 c.cs. of this with titanous chloride, using potassium thiocyanate as indicator, its strength is determined, and as it will retain its strength for a long period, this alum solution may be used in all subsequent cases for standardising the titanous chloride solution. 

M. Major studied the reduction of iron alum by hypophosphites. A. D. Mitchell found that a considerable error is caused by the presence of hypophosphorous acid when ferrous salts are titrated by potassium dichromate. This is tentatively ascribed to the ferrous salt acting as inductor in the oxidation of hypophosphorous acid by chromic acid, probably in virtue of the transient formation... 

Abundant yellow or white salt crusts are present on waste rock and at the surface of the soil. The crusts comprise alum-like sulfate minerals containing variable amounts of sodium, potassium, iron and aluminium, such as the mineral jarosite. They are often very soluble in water, releasing acid and precipitating ferric hydroxides. 

Preparation.—The main source of rubidium compounds is the residual mother-liquor obtained in the extraction of potassium chloride from carnallite. The solution contains rubidium-carnallite, RbCl,MgCI2, a substance transformed by addition of aluminium sulphate into rubidium-alum, RbAl(S04)8,12H20. Separation from the potassium and caesium salts also present is effected by fractional crystallization of the alum,8 of the chloroplatinate 8 Rb2PtCl8, of rubidium-iron-alum,4 and of the double chloride with stannous chloride5 or with antimony trichloride.6... 

Addition of potassium hydroxide to a solution of the alum, and subsequent evaporation yields a crop of crystals yellowish brown in colour and possessing peculiar optical properties like tourmaline. Their composition is given as 5K2S04.2Fe2(S04)2.(0H)2.16H20. The crystals decompose to iron alum and a basic salt. 

Chemical properties of iron. Passivity. Ferrous compounds ferrous sulfate, ferrous ammonium sulfate, ferrous chloride, ferrous hydroxide, ferrous sulfide, ferrous carbonate. Ferric compounds ferric nitrate, ferric, sulfate, iron alum, ferric chloride, ferric hydroxide, ferric oxide (rouge, Venetian red). Potassium ferro-cyanide, potassium ferricyanide, Prussian blue. 

In llraidy s modification, which is stated to give more consistent results, 2 5 g. of very finely divided air-dry cotton is treated with a mixture of 5 c.c. of 10 per cent, copper sulphate (cryst.) and 95 c.c. of an almost saturatcd solution of sodium carbonate and bicarbonate g crystals and 50 g. bicarbonate made up to 1 litre). The cotton is immersed by means of a rod and the air bubbles are allowed to escape the flask is then surrounded with boiling water for exactly three hours. The contents arc filtered off on an asbestos filter and washed first with dilute sodium carbonate solution and then with water. Then the residual cuprous oxide is dissolved by treatment with a solution containing 100 g. of iron alum and 140 g. of concentrated sulphuric acid per litre. Two such treatments usually suffice. The fitter is tben washed with 2 Af-sulphuric acid the combined filtrate and washings arc titrated with A /25 potassium permanganate solution. According to Brissaud the test is affected by air. 

But the admirable researches of Gay-Lussac and of Mitscherlich have established the fact, that in many instances, different compounds assume the same form. Thus, the following substances, and many others, take the form of the cube, tetrahedron, or regular octohedron, which are geometrically connected. Chloride of sodium (sea-salt), chloride of potassium, sal ammoniac bromide of potassium iodide of potassium sulphuret of lead fluoride of calcium bisnlphuret of iron arseniuret of cobalt sulphate of alumina and potash (alum) ammonia alum chrome alum, iron alum sesqnioxide of iron, sesquioxide of aluminum, sesquioxide of chromium. In like manner, other crystalline forms are found to be common to many different compounds, although none occurs so frequently as the cube and its congeners. 

The octahedral, cubic crystals are violet to black in colour, and appear ruby-red in thin layers and J. H. Kastle found that the intensity of the colour is very much reduced at liquid air temp. F. Klocke, C. F. Rammelsberg, C. von Hauer, and J. W. Retgers showed that the crystals are isomorphous with other alums, for they show similar corrosion figures. E. Dittler obtained overgrowth with potassium aluminium sulphate. T. V. Barker found a close connection between parallel overgrowths in chrome-alum, potash-alum, and ammonia-alum and the mol. vols which are respectively 542-2, 541-6, and 552-2. C. von Hauer found that with the introduction of a crystal of iron-alum in a sat. soln. of chrome-alum nearly all the latter separates out while L. de Boisbaudran found that a sat. soln. of basic ammonium aluminium alum does not affect the octahedral faces of the... 

Dissolve the equivalent of one lozenge in 10 ml of hot water. Cool, add 25 ml of O IN silver nitrate, 10 ml of dilute nitric acid and 5 ml of formaldehyde solution. Heat just to boiling and leave on a water-bath until the precipitate has coagulated. Filter, wash the precipitate and titrate the filtrate and washings with O IN potassium thiocyanate, using iron alum as indicator. 1 ml 0 1 N AgNOa = 0 01226 g KCIO3. 

To about 0-4 g of mercury add 20 ml of 1 1 nitric acid, boil until the solution is colourless, cool and dilute. Add potassium permanganate solution until no further decolorisation occurs, removing any excess with a trace of ferrous sulphate and titrate with 0-lN ammonium thiocyanate, at a temperature not exceeding 20°, using iron alum as indicator. 1 ml O IN = 0 01003 g Hg. 

Mix 15 ml of a saturated aqueous solution of potassium chlorate with 5 ml of dilute nitric acid in a 100-ml graduated flask and weigh. Add 10 ml of the spirit of nitrous ether from a pipette, shake and reweigh. Set aside in a moderately warm place for one hour and shake occasionally. Then add 20 ml of 0-1N silver nitrate, shake well and make up to volume with water. Filter, rejecting the first 20 ml of filtrate. To 50 ml of the remainder add 10 drops of iron alum solution and titrate the excess of silver nitrate with O IN potassium thiocyanate. 1 ml 0 1N AgNOa = 0 0225 g ethyl nitrite. 

The dichromate ion oxidises iron(II) to iron(III), sulphite to sulphate ion, iodide ion to iodine and arsenic(III) to arsenic(V) (arsenate). Reduction of dichromate by sulphite can be used to prepare chrome alum, since, if sulphur dioxide is passed into potassium dichromate acidified with sulphuric acid, potassium and chromium(III) ions formed are in the correct ratio to form the alum, which appears on crystallisation ... 

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