Papers by Keyword: Titration

Abstract: Maleic anhydride grafted natural rubber compatibilizer was prepared in molten state using twin screw extruder. Amount of maleic anhydride and initiator, as well as screw rotation were varied according to Box-Behnken experimental design. Titration of acid group from the anhydride function and FTIR spectra analysis were carried out as quantitative and qualitative analysis of grafted MA, respectively. The results showed that the percentages of grafted MA for all samples were ranged from 1.31 to 5.36%. The optimum conditions are predicted at 14.4 phr of MA level, 0.41 phr of BPO level, and 71 rpm screw rotation giving 5.39 ± 0.16% of grafted MA. FTIR spectra showed that the MA and carbonyl functional group were found in the compatibilizer suggested the presence of grafted MA and ring opening reaction.

Abstract: Abstract. The aim of this work was to study molecular and quantitative aspects of metal ion binding to humic substances (HS). The object of our study was characterization of two standards of humic substances (Elliott Soil standard HA 1S102H and Elliott Soil standard FA 2S102F). All samples of IHSS standards HS were characterized by elemental analysis (EA), ultraviolet-visible spectroscopy (UV/Vis), Fourier transform infrared spectroscopy (FTIR) and steady-state fluorescence spectroscopy. Chemical parameters on the complexation of Cu (II), Pb(II) and Hg(II), including the conditional stability constants and the percentage of fluorophores participating in the complexation, were estimated by the modified Stern–Volmer equation. The stability constants (log K_a) of Me(II)–ESHS complexes range from 3.70 to 5.15 in the order: Hg–ESHA>Cu–ESHA>Pb–ESHA>Cu–ESFA>Pb–ESFA. With respect to the ESHA, ESFA, which showed the smallest contents of O-containing functional groups (e.g. hydroxyl, carbonyl, ester, especially carboxyl groups on the aromatic ring) and the lowest humification degree, the ESFA was characterized by much smaller stability constants. Our findings suggest that soil HS belongs to class of important organic ligands for complexation with heavy metal ions and may significantly affect the chemical forms, mobility, bioavailability and ecotoxicity of heavy metals in the soil environment.

Abstract: The kinetics of the reaction is essential for the synthesis of polyurethane. In this study, the reaction kinetics and polymerization conditions in two-step process of isophorone diisocyante (IPDI) and polypropylene glycol (PPG) with organo-tin mixed catalyst were investigated by chemical titration. The results showed that the reaction obeyed the second-order equation of step-growth polymerization, the rate constants of IPDI and PPG reaction at 50, 60 and 70°C were 0.0161, 0.0373 and 0.0806 kg•mol-1•min-1，respectively. The activation energy obtained from the result was 74.25 kJ•mol-1. The polyurethane with number molecular weight 38721 was synthesized and was characterized by Fourier transform infrared (FTIR).

Abstract: The study of polyurethanes are of continuing interest due to their excellent physical properties. In this study, the reaction kinetics and polymerization conditions in two-step process of toluene diisocyante (TDI) and polypropylene glycol (PPG) with organo-tin mixed catalyst were investigated by di-n-butylamine back-titration. It was showed that the reaction obeyed the second-order equation of step-growth polymerization, the rate constants of TDI and PPG reaction at 50, 60 and 70°C were 0.0922, 0.3373 and 0.5828 kg•mol-1•min-1，respectively. The activation energy obtained from the result was 71.63 kJ•mol-1. The number average molecular weight (Mn) and molecular-weight distribution (Mw/Mn) of the polyurethane were 45175 and 1.53, respectively, and the content of hydrogen bonding in the N-H group from Fourier transform infrared spectrum (FTIR) was 80.75%, which manifested that the large amount of N-H were present in hydrogen bonding.

Abstract: By strong alkali (acid) titration strong acid (alkali), alkali (acid) titration mono-weak acid (alkali), precipitation titration and coordination titration to drop by half a drop, and settling the titration error specific terms, to illustrate the macro titration analysis would like to have drop half a drop of a solution. When strong alkali titrate strong acid or monobasic weak acid, there is no need to drop half a drop. As strong acid titrate strong alkali, there is must to drop half a drop as methyl orange for indicator. But phenolphthalein as indicator, there is doesn't need to drop half a drop. Strong alkali titrate monobasic weak acid, there is no need to drop half a drop. Eriochrome Black T for indicator titrate magnesium ion with EDTA, there is must to drop half a drop. Titration of zinc by EDTA, don't need to drop half a drop. Titration chloride ion with Moore method can not drop half a drop.