alpha.- and .beta.-ferric fluoride trihydrate revisited: crystal structure and iron-57 Moessbauer spectra
| Autor: | P. K. Smith, D. G. Karraker |
|---|---|
| Rok vydání: | 1992 |
| Předmět: | |
| Zdroj: | Inorganic Chemistry. 31:1118-1120 |
| ISSN: | 1520-510X 0020-1669 |
| DOI: | 10.1021/ic00032a042 |
| Popis: | Neilsen prepared the two different crystalline forms of Fe-F{sub 3} {center dot} 3H{sub 2}O by evaporation of an HF solution of Fe{sup 3+} at room temperature ({alpha}-form) and above 50C ({beta}-form). Reinvestigation of the two forms of FeF{sub 3} {center dot} 3H{sub 2}O found a surprising correspondence of the crystal structure of {alpha}-FeF{sub 3} {center dot} 3H{sub 2}O with a reported structure of FeF{sub 2} {center dot} 4H{sub 2}O. Also, a T{sub N} of 19.3 K for {beta}-FeF{sub 3} {center dot} 3H{sub 2}O was discovered instead of the reported T{sub N} of 14.7 K. Both results are explained by the difficulty of preparing pure samples of the Fe{sup 2+}-Fe{sup 3+} fluoride hydrates. Both the white {alpha}-FeF{sub 3} {center dot} 3 H{sub 2}O and the pink {beta}-FeF{sub 3} {center dot} 3H{sub 2}O were prepared by Neilsen's method - crystallization from an HF solution of Fe{sup 3+} at room temperature ({alpha}) or above 50C ({beta}). Powder X-ray diffraction patterns showed that, in most cases, the products were mixtures of the two forms. Pure {beta}-FeF{sub 3} {center dot} 3H{sub 2}O was prepared by evaporation to dryness at 80-100C. Precipitation of {alpha}-FeF{sub 3} {center dot} 3H{sub 2}O by mixing a saturated solution with coldmore » ethanol was, at times, successful in preparing pure {alpha}-form material, but more often this method also produced mixtures. No reliable method was found for preparing pure {alpha}-form samples. All preparations were characterized by X-ray diffraction. Nine samples of both forms were analyzed. Anal. Calcd: Fe, 33.45; F, 34.17. Found: Fe, 33.80 (42); F, 34.09 (59).« less |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|