Iron ammonium alum potassium sulphate

Mitscherlich also measured the angles of the crystals of double sulphates of potassium and ammonium with magnesium, ferrous iron, manganese, zinc, copper, cobalt and nickel. This established the isomorphism of potassium and ammonium sulphates. He found that the double potassium sulphates had one proportion of water more than the double ammonium sulphates, and also obtained a salt crystallising in beautiful and large octahedra with exactly the same composition as alum but containing ferric oxide instead of alumina (ferric alum). He says he hoped to show that a study of crystallisations would give the compositions of bodies as certainly and definitely as chemical analysis . A letter from Humboldt to Mitscherlich said this beautiful work had exposed the incorrectness of Haiiy s view. ... 

A number of dilute chemical solutions attack tin metal slowly, with consequent corrosion. Among these are aluminium chloride, aluminium potassium alum, ammonium sulphate, hydrochloric acid, hydrobromic acid, hydriodic acid, fluorine, chlorine, bromine, iodine, iron(III) chloride, potassium carbonate, potassium hydroxide, silver nitrate, zinc chloride, glycerol and maleic acid. ... 

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... 

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. 

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