6505-50-6Relevant academic research and scientific papers
Non-isothermal dehydration and decomposition of dl-lactates of transition metals and alkaline earth metals: A comparative study
Verma,Verma,Chandra,Bhushan
, p. 351 - 354 (2008/10/09)
A comparative study of the non-isothermal decomposition of the dl-lactate hydrates of magnesium, calcium and strontium has been made with that of the dl-lactate hydrates chromium(III), manganese(II), iron(II), cobalt(II), nickel(II), copper(II) and zinc(II) keeping dry air as the purge gas and the heating rate maintained at 10 K min-1. While the dl-lactates of manganese(II), cobalt(II) and copper(II) followed single step decomposition scheme suggesting that dehydration and decomposition steps overlapped, the dehydration steps of the other compounds were distinct. à-T plots of none of the dehydration steps showed any induction period, indicating no physical desorption, nucleation or branching. Neither the à max-values nor the onset temperatures of the dehydration steps did show any pattern. The TG data of the dehydration steps have also been analyzed using the Freeman-Carroll, Horowitz-Metzger, Coats-Redfern, Zsakó, Fuoss-Salyer-Wilson and Karkhanavala-Dharwadkar methods. Values of order of reaction, activation energy and Arrhenius factor have been approximated and compared. There are similarities in the activation energy values for the dehydration steps (-1 in general). It is higher with group 2 metals and lower in transition metals (maximum in magnesium and lowest in chromium and iron lactates). In cases of overlapping of dehydration and decomposition steps, the activation energy values are on the lower side with the same trend (lower in cobalt and copper cases).
Thermoanalytical studies on the non-isothermal dehydration and decomposition of dl-lactates of a series of transition metals
Verma, Ranjit K.,Verma, Lata,Chandra, Mukesh
, p. 2982 - 2987 (2007/10/03)
The non-isothermal decomposition of a series of dl-lactate hydrates of chromium(III), manganese(II), iron(II), cobalt(II), nickel(II), copper(II) and zinc(II) has been studied with dry air as the purge gas and heating rate programmed at 10 Kmin-1. The α-T plots obtained from the TG data of none of the purely dehydration steps and the decomposition steps of cobalt(II) and zinc(II) compounds show any induction period, indicating no physical desorption, nucleation or branching while the α-T plots of the other decomposition phenomena show a period of induction indicating that physical desorption and nucleation are taking place. The TG data of the dehydration steps have also been analyzed using various differential, difference-differential, and integral methods, viz., Freeman-Carroll, Horowitz-Metzger, Coats-Redfern, Zsako, Fuoss-Salyer-Wilson and Karkhanavala-Dharwadkar methods. Values of activation entropy, Arrhenius factor, and order of reaction have been approximated and compared. The values of activation energy (E) for the dehydration steps are less than 60 kJmol -1 as expected for removal of weakly bound water of crystallization from such compounds. The entropy of activation (ΔS#) values have high magnitude in each case (-1mol-1) indicating an appreciable degree of rearrangement.
