Use of Boron Phosphate in the Solid‐State Preparation of Crystalline Iron(III) Phosphate and Manganese(II) Diphosphate

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The possibility of using BPO4 for the solid‐state preparation of crystalline phosphates of trivalent iron, manganese, and chromium has been investigated. If BPO4 and Fe2O3 are heated at 900°C, a complete conversion of BPO4 to the quartz form of FePO4 results after 9 h. If FeCl3.6H2O is used instead of Fe2O3, a multiphase crystalline product is obtained in which the dominant phase is the quartz form of FePO4. The reaction of BPO4 with Mn2O3 or MnO2 at 830°C yields Mn2P2O7; the amount of conversion of BPO4, to Mn2P2O7 after 4 h is 80% (if Mn2O3 is used) and 75% (if MnO2 is used). However, the method is not successful in the preparation of phosphates of chromium: the reaction of BPO4 and some chromium compounds yields α‐Cr2O3 as the only chromium‐containing product.