On Solid Solution Formation in the Cu(HCOO)2-Co(HCOO)2-H2O System

✍ Scribed by D. Stoilova

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 285 KB
• Volume: 104
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1993.1176

✦ Synopsis

Solubility in the (\mathrm{Cu}(\mathrm{HCOO}){2}-\mathrm{Co}(\mathrm{HCOO}){2}-\mathrm{H}{2} \mathrm{O}) system has been studied at 25 and (50^{\circ} \mathrm{C}). Three series of solid solutions are formed in the system at (50^{\circ} \mathrm{C}) : solid solutions having the (\mathrm{Co}\left(\mathrm{HCOO}{2} \cdot 2 \mathrm{H}{2} \mathrm{O}\right.) crystal structure as a matrix and solid solutions having the (\mathrm{Cu}(\mathrm{HCOO}){2} \cdot 2 \mathrm{H}{2} \mathrm{O}) crystal structure as a matrix. It was established that the crystal structure of the monoclinic (\mathrm{Cu}(\mathrm{HCOO}){2} \cdot 2 \mathrm{H}{2} \mathrm{O}) undergoes a change into a new crystal structure (solid solutions) in the concentration range (\mathrm{Cu}{0.23} \mathrm{CO}{6.13}\left(\mathrm{HCOO}{2}\right.). (2 \mathrm{H}{2} \mathrm{O}-\mathrm{Cu}{0.74} \mathrm{Co}{0.26}(\mathrm{HCOO}){2} \cdot 2 \mathrm{H}{2} \mathrm{O}). The same phenomenon was observed in the (\mathrm{Cu}(\mathrm{HCOO}){2}-) (\mathrm{Mg}(\mathrm{HCOO}){2}-\mathrm{H}{2} \mathrm{O}) system at (50^{\circ} \mathrm{C}). The X-ray diffraction spectra of the samples (\mathrm{Cu}{0.74} \mathrm{Co}{0.26}\left(\mathrm{HCOO}{2}\right.). (2 \mathrm{H}{2} \mathrm{O}) and (\mathrm{Cu}{0.73} \mathrm{Mg}{0.27}(\mathrm{HCOO}){2} \cdot 2 \mathrm{H}{2} \mathrm{O}) are proved to be identical. Since the new crystal phase contains a copper formate dihydrate as a main component a hypothesis has been made that a new polymorphous modification of (\mathrm{Cu}(\mathrm{HCOO}){2} \cdot 2 \mathrm{H}{2} \mathrm{O}) is probably formed due to included cobalt and magnesium ions in the copper formate dihydrate crystal structure. The new polymorphous modification of (\mathrm{Cu}(\mathrm{HCOO}){2}). (2 \mathrm{H}{2} \mathrm{O}) is supposed to be built up by the structural element (\mathrm{Cu}(\mathrm{HCOO}){4}\left(\mathrm{H}{2} \mathrm{O}\right){2}). Two type of solid solutions are formed in the (\mathrm{Cu}(\mathrm{HCOO}){2}-\mathrm{Co}(\mathrm{HCOO}){2}-\mathrm{H}{2} \mathrm{O}) system at (25^{\circ} \mathrm{C}) : solid solutions based on (\mathrm{Cu}(\mathrm{HCOO}){2} \cdot 4 \mathrm{H}{2} \mathrm{O}) and solid solutions based on (\mathrm{Co}(\mathrm{HCOO}){2} \cdot 2 \mathrm{H}{2} \mathrm{O}). Cobalt formate dihydrate retains its crystal structure up to a maximum of (50 \mathrm{~mol} %) copper formate. 1993 Acadentic Press, Inc.