Ferric alums

Add a known volume ofo oaM.AgNOj solution (in excess) and boil the solution until the silver chloride has coagulated. Filter through a conical 5 cm. funnel, ensuring that the filter-paper does not protrude above the r m of the funnel. Wash the silver chloride and the filter-paper several times with a fine jet of distilled water. To the united filtrate and washings add i ml. of saturated ferric alum solution. The solution should be almost colourless if it is more than faintly coloured, add a few drops of concentrated nitric acid. Then titrate with 0 02M-ammonium thiocyanate solution until the permanent colour of ferric thiocyanate is just perceptible. (Alternatively the chloride may be determined potentiometrically.)... 

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. 

F-test 140, (T) 841 Faraday constant 60, 504 Faraday s laws 503, 504 Fast sulphon black F 319 Fats D. of saponification value, (ti) 308 Ferric alum indicator see Ammonium iron(III) sulphate... 

Synonyms ferric ammonium sulfate ammonium ferric sulfate iron alum ferric alum ferric ammonium alum... 

In 1863 R. C. Bottger of Frankfort-on-the Main found that thallium occurs in some spring waters. A certain salt mixture from Nauheim contained, in addition to the chlorides of sodium, potassium, and magnesium, those of cesium, rubidium, and thallium. Since he was able to prepare a thallium ferric alum exactly analogous to potassium ferric alum, he regarded thallium as an alkali metal (72, 73). Although it is sometimes univalent like sodium and potassium, it is now classified in Group III of the periodic system. 

The 0.15N Ferric Alum soln shall be prepd as specified in Standard MIL-STD-286, method603.1 4.3 1.2.3 Procedure. An accurately weighed portion of approx O.lg of sample shall be transferred to a 500-nl titration flask. Twenty-five ml of distd w shall be added and shaken and heated until the sample is dissolved completely. The titration flask shall be placed with a magnetic stirrer and the contents shall be stirred for at least 10 mins. The air shall be swept out with a stream of carbon dioxide and the carbon dioxide atm shall be maintained thruout the detn. Exactly 50ml of 0.2N chromous chloride soln shall be added to the 500ml titration flask. The contents shall be stirred for 5 mins and 25mi of i5 percent HCi shall be added. Ten drops of 2% aq phenosafranin indicator shall be... 

N = normality of ferric alum soln Note Illustration of Apparatus for Storing and Using Titanous Chloride Solution is on p D1647 of Vol 5. On p D1646-L is stated that Mr N,... 

The purity of the crystallized product, determined volu-metrically by Volhard s method, exceeds 98%. In this procedure, 10 ml. of a 1% solution of methylisourea hydrochloride is acidified with a few drops of nitric acid and treated with 20 ml. of 0.1 N silver nitrate. After removal of the silver chloride by filtration, the excess of the silver nitrate is estimated with 0.1 TV thiocyanate solution, using ferric alum as indicator. Alternatively, 10-ml. portions of 0.1 N silver nitrate, acidified with nitric acid, may be titrated directly with the 1% methylisourea hydrochloride solution in the presence of tartrazine. 

Chlorides, bromides, and iodides can be quantitatively determined by treatment with silver nitrate, and, with suitable precautions, the precipitated halide is washed, dried, and weighed. Chlorides in neutral soln. can be determined by F. Mohr s volumetric process 27 by titration with a standard soln. of silver nitrate with a little potassium chromate or sodium phosphate as indicator. When all the chloride has reacted with the silver nitrate, any further addition of this salt gives a yellow coloration with the phosphate, and a red coloration with the chromate. In J. Volhard s volumetric process, the chloride is treated with an excess of an acidified soln. of silver nitrate of known concentration. The excess of silver nitrate is filtered from the precipitated chloride, and titrated with a standard soln. of ammonium thiocyanate, NH4CN8—a little ferric alum is used as indicator. When the silver nitrate is all converted into thiocyanate AgN03-fNH4CNS=AgCNS +NH4NOS, the blood-red coloration of ferric thiocyanate appears. 

Yolumetrically, thiocyanate is estimated by Volhard s method, which involves titration with standard silver nitrate solution containing nitric acid, ferric alum being used as indicator. Cuprous thiocyanate dissolved in ammonium hydroxide solution and acidified with dilute sulphuric acid may be titrated with permanganate.6 An iodometrie method has also been described.7... 

Ferric Ammonium Sulphate Ammonio-Ferric Alum) FeNH (S04)s + 12H20. Mol. Wt. 482.28. 

Foreign Bodies which Reduce Permanganate when Zinc Oxide is Dissolved in Dilute Sulphuric Acid. — Very carefully Iril unite 3 gm. of zinc oxide, in a mortar with 20 cc. of water conluining in solution 0.2 gin. of pure ferric alum free from ferrous salt. Then add to the mixture. 25 cc. of diluted sulphuric acid, and effect complete solution by gently heating. 

Dissolve approx O.lg of RDX, in a 500 ml titration flask, with a mixt of 25 ml of glac AcOH and 25 ml of coned. HC1. Stir the contents of the flask for at least 10 mins using a magnetic stirrer while the air is being replaced with COz. Maintain a C02 atm throughout the determination. Add exactly 100 ml of 0.2N chromous chloride soln and stir for another 15 mins. Add 15 drops of phenosafranine indicator and titrate with 0.15N ferric alum soln. The end-point is a sharp color change from green to blood-red. Determine a blank and caluclate as follows ... 

The absorption is complete in about one hour. The pyridine and its methiodide are then washed out with water, acidified with nitric acid, a known volume of silver nitrate added and the excess of the latter estimated by thiocyanate, using ferric alum as indicator. 

This energetic reducing agent can be maintained at constant strength in aqueous hydrochloric acid solution for a reasonable period. It is advisable, however, to re-standardise it after 24 hours standing. It serves for the reduction of aromatic nitro compounds, some nitroso bodies, many azo dyes, and of nearly all the dyes which yield leuco-compounds. It is easily standardised against a ferric salt—say ferric alum—using potassium thiocyanate as indicator. From the equations —... 

Example of (3).—0 99 gm. of Chrysophenine G (C30H26N4O8SaNa2) is dissolved in a litre of water. 100 c.cs. of this solution are withdrawn and boiled, with a current of carbon dioxide passing through 10 c.cs. of cone, hydrochloric acid and 50 c.cs. of titanous chloride are then added, and the mixture boiled until the precipitate dissolves and the solution turns a slight violet colour. After cooling, the excess of titanous chloride is titrated with ferric alum. 

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