A method for the determination of lathanum, praseodymium, neodymium and samarium oxides in cerium dioxide has been developed.
The sample in the oxalate form is mixed with the binding material (boric acid) in the ratio 1∶1 pressed to form a double layer
pellet over a boric acid backing pellet and irradiated by X-rays from a tungsten tube. The secondary X-rays are dispersed
with a LiF (200) crystal in a Philips PW 1220 semiautomatic X-ray fluorescence spectrometer. The intensity of fluorescent
X-rays is measured by a flow proportional counter. The minimum determination limit is 0.01% for lanthanum and samarium oxides
and 0.02% for praseodymium and neodymium oxides. The precision at each concentration of the standards and theoretical minimum
determination limit for each element have been calculated.
Authors:A. Souza, M. Oliveira, I. Santos, M. Conceição, L. Nunes, and J. Machado
The kinetics of thermal decomposition of solid In(S2CNR2)3 complexes, (R=CH3, C2H5, n-C3H7,i-C3H7, n-C4H9 and i-C4H9), has been studied using isothermal and non-isothermal thermogravimetry. Superimposed TG/DTG/DSC curves show that thermal
decomposition reactions occur in the liquid phase, except for the In(S2CNMe2)3 and In(S2CNPri2)3 compounds.
Authors:L. Machado, A. Marins, E. Muri, A. Biondo, J. Matos, and I. Mazali
Reactions in aqueous-alcoholic solution between diphenyl-4-amine barium sulphonate (Ba-DAS—anionic surfactant) and the hydrated
sulphates of Fe(III) and Fe(II) ions and their use to ovtain iron oxides are described here. The formation of Fe(II) complexes
was reached by using an excess of Ba-DAS, in absence of light under inert atmosphere. The complexes achieved Fe2[(C12H10NO3S)4]·9H2O and Fe3[(C12H10NO3S)6]·12H2O were characterized by TG/DTG and IR, UV-VIS and 57Fe-Mössbauer analyses.