Iron ammonium alum oxides

Iron metal, wire III Q. 73 Ferric ammonium alum XI Ferric chloride II, III Ferric oxide XI... 

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. 

Earlier, Turrentine (Ref 4) obtained ferric azide in soln by electrolysis of a dil sodium azide soln using iron electrodes and later by Browne et al (Ref 6) on using iron electrodes in liq amm solns of ammonium azide, but the product was ammonolyzed to an Ammono-Basic Ferric Azide. Curtius et al (Refs 1 2), with ferric alum and NaN, obtained ferric azide in soln and they also repotted that iron dissolved in dil aq hydrazoic acid to form the azide, but the soln decompd on evapn giving either the basic azide or hydroxide. In 1934 Franklin (Ref 9) noted that aq hydrazoic acid reacts on iron to form ferric azide, nitrogen and ammonia together with a small amt of hydrazine. According to Franklin Ferrous Azide, Fe(Nj), is formed first and oxidizes to ferric azide when the soln is warmed with excess hydrazoic acid present. Ricca (Ref 11) studied the reactions of the ferric ion with hydrazoic acid on electrolysis of their solns and obtained results which would indicate that ferric azide has the structure [Fe(Nj)](Nj)2... 

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. 

A more refined test is the Schultz (1924) method for cholesterol, which involves the application of a mixture of concentrated sulfuric acid and glacial acetic acid to sections which have been oxidized with ferric ammonium sulfate (iron alum). A blue-green color results. The iron alum apparently oxidizes 3-hydroxy steroids and their esters to 7-oxy steroids, which give the Lifschlltz color reaction on the application of the acids. (Fieser and Fieser, 1949, p. 234). This test is considered to be more specific for a limited group of steroids than is the sulfuric acid method cited above, which reveals a large number of unsaturated polycyclic compounds. Recently, however, Kent (1952) has reported that a positive reaction also occurs with carotene. 

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. ... 

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