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Properties of Solids
Published in W. M. Haynes, David R. Lide, Thomas J. Bruno, CRC Handbook of Chemistry and Physics, 2016
W. M. Haynes, David R. Lide, Thomas J. Bruno
Potassium chlorate Potassium perchlorate Potassium chromate Potassium chrome alum Potassium dideuterium arsenate (KDDA) Potassium dideuterium phosphate (KDDP) Potassium fluoride Potassium dihydrogen arsenate (KDA) Potassium dihydrogen phosphate (KDP)
Leaching with Acids
Published in C. K. Gupta, T. K. Mukherjee, Hydrometallurgy in Extraction Processes, 2019
Chromium in nature occurs in oxide form in a large variety of minerals, but the principle ore-forming mineral is chromite which has the ideal composition of FeO⋅ Cr2O3 with 68% Cr2O3 and 32% FeO. Actually, the Fe/Cr ratio in the mineral varies considerably and is associated with other elements such as Al and Mg. Chromite is, therefore, better represented by the general formula (MgFe)O(Cr,Fe,Al)2O3. Chromite ores are generally classified into three grades depending on the Cr2O3 content, namely, metallurgical (>46% Cr2O3), chemical (40 to 46% Cr2O3), and refractory (60% Al2O3 and Cr2O3). The metallurgical-grade chromite should have a Cr/Fe ratio of greater than 2:1, while the chemical-grade ratio should range from 1.5:1 to 2:1. The sulfuric acid-leaching process for metallurgical/chemical grade finds application11 in the production of pure chrome alum [(NH4)2·SO4·Cr2(SO4)3·24H2O] which is subjected to electrolysis for the preparation of pure chromium metal. The chrome ore is ground wet to less than 45 µm and then digested with H2SO4 of 40 to 45% concentration mixed with 2 to 3% chromic acid. The lixivant is formed by putting together 93% H2SO4 acid and anolyte from the electrolytic cell. Presence of chromic acid helps to catalyze the digestion reaction as shown below: () Cr2O3⋅FeO+4H2SO4→Cr2(SO4)3+FeSO4+4H2O
Advances in coordination chemistry of hexaurea complexes of chromium(III)
Published in Journal of Coordination Chemistry, 2020
Ritu Bala, Diksha Sachdeva, Manoj Kumar, Vinit Prakash
Therefore, this versatile ligand, urea shows various potential applications in the form of hexaurea chromium(III) complex ion. Hexaureachromium(III) complex ions help in the development of inorganic chemistry by stabilizing various complex anions as anion receptors and possess supramolecular features [52–54]. Supplementation of a GTF-deficient diet with chromium (in the form of hexaureachromium(III) chloride or a neutralized solution of chrome alum) has resulted in a significant increase of intravenous glucose tolerance [55]. The complex cation [Cr(OC(NH2)2)6]3+ is expected to have octahedral symmetry with the urea ligands being coordinated to the central Cr3+ through oxygens (Scheme 1(a)).