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Abstract  

The solid complexes of Cr(NO3)3 with L-α-amino acids (AA=Val, Leu, Thr, Arg, Phe and Try) have been prepared in 95% alcoholic, the compositions of which were identified as the general formula Cr(AA)2(NO3)32H2O by elemental and chemical analyses. The bonding characteristics of the title complexes were characterized by IR, indicating that nitrogen and oxygen atoms in the ligands coordinated to Cr3+ in a bidentate fashion. With the aid of TG-DTG and IR techniques, the complexes were subjected to thermal decomposition in an atmosphere of oxygen, presuming that the decompositions of the complexes consist of two steps and the complexes were decomposed into chromium hemitrioxide after undergoing dehydration and skeleton splitting of the complexes. The constant volume energies of combustion of the complexes were determined by a RBC-P type rotating-bomb calorimeter. According to Hess's law, the standard enthalpies of formation of the complexes were calculated as (-1831.404.40), (-2542.036.13), (-1723.813.99), (-2224.313.02), (-2911.616.53) and (-659.327.42) kJ mol-1, respectively.

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synthesized by the proteic sol–gel method [ 9 , 10 ], using as precursor materials aluminum, manganese, cobalt, and chromium nitrates (P.A.). Figure 1 shows the flowchart of the synthesis process. In this method, the precursors are mixed with filtrate

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, which takes place in the pores of the silica matrix at the heating of the gels. As it results from the weak exothermic effect registered on DTA curve of gel CrPGSi ( Fig. 2 ), chromium nitrate reacts with 1,3-propanediol around 70 °C, leading to a

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chromium nitrate and PVA is complete. Thus, no exothermic process takes place in the range 100–200 °C. The decomposition of this product takes place in the range 250–400 °C with a strong asymmetric exothermic effect, revealing a superposition of exothermic

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