Móssbauer spectra at 77°K have identified the precipitated gel formed by the interaction of TiCI3 and H3Fe(CN)6 solutions as a ferrocyanide, Ti4+[Fe(CN)6]4-, resulting from a redox reaction. The isomer shift (5 = -0.06 mm/sec) and quadrupole splitting ( 0) are identical (based on a computer curve-fit program) with those from a sample of Ti4+[Fe(CN)s]4-made by the direct interaction of TiCl, and H4Fe(CN)6 solutions. The precipitated gel formed from TiCl3 and [H4Fe(CN)6] gave = -0.01 and = 0, and corresponds to Ti3+4[Fe(CN)6]4-3, which is expected in the absence of a redox reaction. Móssbauer spectra for Fe2+3[Co(CN)6]3-2 exhibited double quadrupole splitting. The peak for = 2.81 is attributed to four Fei2+ ions in the 4b positions of Fm3m, whereas the peak for = 1.82 is attributed to two Fen2+ ions statistically distributed in the 8c positions. For the first time it has been shown that the two kinds of Fe2+ ions are actually in a different environment. Móssbauer spectra of the so-called Prussian and Turnbull's blue, which have been aged under water for 10 min or more and selectively enriched in 57Fe to obviate severely overlapping Móssbauer absorption peaks, have confirmed the work of earlier investigators on unenriched samples. Both of the blue gels which have contacted water for less than 30 min after the precipitation step have been found to be amorphous by electron diffraction, whereas longer aged samples are crystalline. It is suggested that Móssbauer spectra for such gels aged for periods much less than 10 min would throw light on this rapid aging phenomenon.
Fällung der Trihydroxide von "lAm und 244Cm (55% 244Cm) aus wäßrigen Lösungen führt zu sehr kleinen (10‐20 Å 9) amorphen Teilchen, deren Alterung in Wasser zur Bildung stabförmiger kristalliner Strukturen (isomorph mit den hexagonalen Lanthanid‐trihydroxiden) führt.
Freshly precipitated cupricoferrocyanide gel i s composed of finely divided particles in the range of 10 A which exhibit amorphous x-ray and electron diffraction patterns. On aging in contact with water $t room temperature, the gel becomescrystalline (Fm3m, a, = 10.013+0.001 A ) within 10 to 15 minutes after precipitation. After aging for 20 hours, platelike material exhibiting sharp edges begins to form. Orientation of this sheetlike macerial i s aided by allowing it to dry on a mercury surface.Concurrent with the formation of :his sheetlike material, there appear larger d/n values in the range of 10 A (verified by both x-ray and electron diffraction patterns). These extza lines (corresponding approximately to a cubic unit cell, where a. = 20.0 A) can be removed by dehydration processes. Dehydration isobars for this sheetlike material yield a sharp step corresponding to a loss of 6-8 moles of water per mole of cupric ferrocyanide. When the sheetlike material is not present, continuous isobars a r e obtained. With loss of water, the cupric ferrocyanide changes from reddish-brown to a bluish color Additional large spacings (apparently corresponding to a double unit cell) and color changes (on dehydration) have also been observed for well-aged Co3[Fe(CN)6]2 (bluereddish-violet), Ni3[Co(CN)6]2 (bluegreen), and CO3[CO(CN)6]2 (roseblue).
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