Thermochemistry of Gd2BaCuO5 and LuBa2Cu3Ox

Solution calorimetry, using 6.0 M HCl as a solvent, is used to study the thermochemistry of Gd2BaCuO5 and the high-temperature superconductor LuBa2Cu3O6.92. For the first time, the standard formation enthalpies of these phases have been determined as follows: DeltafH(o)(Gd2BaCuO 5, s, 298.15 K) = -2618.6 +/- 7.4 kJ/mol; DeltafH(o)(LuBa2Cu3O6.92, s, 298.15 K) = -2693.1 +/- 11.9 kJ/mol. The thermodynamic stability at room temperature has been assessed. The results show that Gd211 and Lu123 are thermodynamically stable with respect to binary oxides and unstable with respect to interaction with CO 2 at ambient temperatures. Lu123 is thermodynamically stable with respect to assemblages containing combinations of Lu2O3, CuO, and BaCuO2 and thermodynamically unstable with respect to interactions with water.     

Development and validation of a sensitive and fast solid-phase spectrophotometric procedure for phenol determination in pharmaceuticals

A very sensitive, simple, and fast solid-phase spectrophotometric procedure for the determination of phenol using the p-nitrobenzenediazonium reagent (DAR reagent) was developed. This procedure is based on the simultaneous concentration of the orange product on a Dowex 1-X2 anion exchanger within 15 min, and a direct absorbance measurement of the sorbed species at both 530 nm (the absorption maximum of the phenol-DAR in the resin phase) and 700 nm (the range where only the resin absorbs light). Quality control and evaluation of the analytical parameters was carried out using a comprehensive prevalidation strategy. The linearity of the method was confirmed within an analyte working range from 0.01 to 0.10 μmol (0.2 to 2.0 nmol mL(-1)). The precision ranged from ±1.17 to ±9.61%; the accuracy ranged from -17.50 to +17.81%. The evaluated limiting values were L(D) = 0.0013 μmol and L(Q) = 0.0082 μmol. The DAR-SPS method was successfully applied to the determination of phenol in a pharmaceutical sample of salicylic acid (98.0-100.0%) and vaccines (98.0-103.4%).     

Radiological,structural and chemical characterization of raw materials and ceramic tiles in Serbia

Journal of Radioanalytical and Nuclear Chemistry - This paper presents the results of the gamma spectrometric analysis of 27 raw materials used for the production of ceramic tiles in Serbia and 9...     

Radioactivity of building materials in Serbia and assessment of radiological hazard of gamma radiation and radon exhalation

Journal of Radioanalytical and Nuclear Chemistry - This paper presents a gamma spectrometric analysis of 47 samples of building materials produced and used in Serbia. Based on the measured activity...