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Über die Hydrolyse von Eisen(III)Salzlösungen. I. Die Hydrolyse der Lösungen von Eisen(III)chlorid
Author(s) -
Feitknecht Walter,
Giovanoli Rudolf,
Michaelis Werner,
Müller Max
Publication year - 1973
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19730560820
Subject(s) - chemistry , hydroxide , chloride , deprotonation , base (topology) , precipitation , ion , amorphous solid , octahedron , inorganic chemistry , crystallography , hydrolysis , polymer chemistry , organic chemistry , mathematical analysis , physics , mathematics , meteorology
When a very diluted iron(III)chloride solution is slowly alkalified by a weak base, the deprotonation of [Fe(H 2 O) 6 ] 3+ proceeds in a first stage to form mono‐ and dinuclear hydroxoaquo‐complexes. In a second stage 4 dimers condense around a chloride ion to form an eight membered ring, an embryon, which grows fast to very small crystals of the composition Fe 4 O 3 (OH) 5 Cl and the structure of the β‐FeOOH. These crystalline micells remain colloidally dissolved. If the pH is raised above approximately 3.4 the Cl − ‐ are exchanged against OH − ‐ions and flocculation occurs. This shows that Pauli , assuming the micells of such sols to be polynuclear complex ions, is basically correct, and it follows that micells can also be micro‐crystals. When an iron(III)chloride solution is neutralized fast with a strong base, an ‘amorphous’ precipitation is obtained which gives with MoK α ‐X‐rays only two broad reflections, showing that the iron oxide hydroxide octahedra are condensed in a highly disordered way. The coherently scattering areas of this precipitate are probably tetramers. Small amounts of primarily formed amorphous iron(III)hydroxide are transformed into β‐FeOOH.