{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,4]],"date-time":"2026-06-04T04:12:48Z","timestamp":1780546368803,"version":"3.54.1"},"reference-count":46,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2021,1,23]],"date-time":"2021-01-23T00:00:00Z","timestamp":1611360000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Minerals"],"abstract":"<jats:p>Iron(II)oxalate dihydrate FeC2O4 \u00d7 2 H2O\u2014humboldtine is not only an important synthetic intermediate, but also a key building block for the preparation of various advanced materials. Interestingly, FeC2O4 \u00d7 2 H2O can be transformed readily into phase-pure siderite FeCO3. The importance of siderite for earth sciences, in particular for the understanding of the deep carbon cycle of our planet, is paramount. The availability of high-quality single crystals of FeC2O4 \u00d7 2 H2O is crucial for diffraction or spectroscopic studies at high pressure. The present article describes a versatile synthetic approach to single crystals of FeC2O4 \u00d7 2 H2O and its deuterated analogue starting from metallic iron together with a complete characterization of the products obtained. The same protocol has been employed successfully for the preparation of 57FeC2O4 \u00d7 2 H2O, as required for M\u00f6\u03b2bauer spectroscopy. In addition, the pressure-dependence of the crystal and molecular structure of the title compound was investigated up to p \u2265 20 GPa.<\/jats:p>","DOI":"10.3390\/min11020113","type":"journal-article","created":{"date-parts":[[2021,1,25]],"date-time":"2021-01-25T09:59:40Z","timestamp":1611568780000},"page":"113","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":21,"title":["Iron(II)oxalate Dihydrate\u2014Humboldtine: Synthesis, Spectroscopic and Structural Properties of a Versatile Precursor for High Pressure Research"],"prefix":"10.3390","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-0249-1646","authenticated-orcid":false,"given":"Harald","family":"M\u00fcller","sequence":"first","affiliation":[{"name":"ESRF\u2014The European Synchrotron, CS 43220 CEDEX 9, F-38000 Grenoble, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"L\u00e9a","family":"Bourcet","sequence":"additional","affiliation":[{"name":"ESRF\u2014The European Synchrotron, CS 43220 CEDEX 9, F-38000 Grenoble, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8904-5461","authenticated-orcid":false,"given":"Michael","family":"Hanfland","sequence":"additional","affiliation":[{"name":"ESRF\u2014The European Synchrotron, CS 43220 CEDEX 9, F-38000 Grenoble, France"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2021,1,23]]},"reference":[{"key":"ref_1","first-page":"207","article-title":"Note sur une combinaison de l\u2019acide oxalique avec le fer trouv\u00e9 a Kolowserux, pr\u00e9s Belin, Boh\u00eamia","volume":"18","year":"1821","journal-title":"Ann. 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