The coagulation of positively charged sol of hydrous ferric oxide of different average sizes for potassium sulphate has been studied in the presence of glucose and urea which stabilise the sol. The degree of stabilisation increases with the fineness of dispersed particles. It has been concluded that the adhesive tendency of the surface of dispersed particles decreases in the presence of said non-electrolytes leading to a decrease in the frequency of collisions resulting in stabilisation. The stability ratioW increases in the presence of glucose and urea for the same amount of the coagulant.
Zusammenfassung Die Koagulation positiv geladener Sole von wäßrigem Ferrioxid verschiedener mittlerer Partikelgrößen mit Kaliumsulfat wird in Gegenwart von Glykose und Harnstoff, die beide das Sol stabilisieren, untersucht. Der Grad der Stabilisierung hängt von der Teilchengröße ab. Es wird geschlossen, daß die Adhäsionstendenz der Oberflächen der dispergierten Partikel in Gegenwart besagter Nichtelektrolyte abnimmt und so zur Abnahme der Kollisionshäufigkeit und damit zur Stabilisierung führt. Das StabilisierungsverhältnisW wächst in Anwesenheit von Glykose und Harnstoff für gleiche Beträge des Koagulators.
The first, highly two-photon active C60 derivative comprised of a A-sp3-D conjugate structure was synthesized showing effective two-photon absorption cross-sections (sigma 2' = 196 x 10(-48) cm4 sec-1 molecule-1) in the nanosecond regime among the best values for diphenylaminofluorene-based AFX chromophores. 相似文献
Interpolation methods such as the nudged elastic band and string methods are widely used for calculating minimum energy pathways and transition states for chemical reactions. Both methods require an initial guess for the reaction pathway. A poorly chosen initial guess can cause slow convergence, convergence to an incorrect pathway, or even failed electronic structure force calculations along the guessed pathway. This paper presents a growing string method that can find minimum energy pathways and transition states without the requirement of an initial guess for the pathway. The growing string begins as two string fragments, one associated with the reactants and the other with the products. Each string fragment is grown separately until the fragments converge. Once the two fragments join, the full string moves toward the minimum energy pathway according to the algorithm for the string method. This paper compares the growing string method to the string method and to the nudged elastic band method using the alanine dipeptide rearrangement as an example. In this example, for which the linearly interpolated guess is far from the minimum energy pathway, the growing string method finds the saddle point with significantly fewer electronic structure force calculations than the string method or the nudged elastic band method. 相似文献
The kinetics of the mercury(II) catalysed ligand exchange of the hexacyanoferrate(II) complex with the N-methylpyrazinium ion (Mpz+) in a potassium hydrogen phthalate buffer medium has been investigated at 25.0 ± 0.1 °C, pH = 5.0 ± 0.02 and ionic strength, I = 0.1 M (KNO3). The reaction was followed spectrophotometrically in the aqueous medium by measuring the increase in absorbance of the intense blue complex [Fe(CN)5Mpz]2– at its max 655 nm. The effect of pH, and the concentrations of [Fe(CN)64–] and Mpz+ on the reaction rate have been studied and analysed. The varying catalytic activity of mercury(II) as a function of concentration has also been explained. The kinetic data suggest that substitution follows an interchange dissociative (Id) mechanism and occurs via formation of a solvent-bound intermediate. The effects of the dielectric constant of the medium on the reaction rates have been used to visualize the formation of a polar activated complex and an interchange dissociative mechanism for the reaction. A mechanism has been proposed in order to interpret the kinetic data. Kinetic evidence is reported for the displacement of CN– by Mpz+ in [Fe(CN)64–]. Activation parameters for the catalysed and uncatalysed reaction have been evaluated, and lend further support to the proposed mechanism. 相似文献
The nucleophilic substitution reaction under NH3 chemical ionization (CI) conditions in cis- and trans-1,2-dihydroxybenzosuberans (1–4) has been studied with the help of ND3 CI and metastable data. The results indicate that in the parent diols 1 (cis) and 2 (trans), the substitution ion [MsH]+, is produced mainly by the loss of H2O from the [MNH4]+ ion (SNi reaction) while in their 7-methoxy derivatives 3 and 4, the ion-molecule reaction between [M? OH]+ and NH3 seems to be the major pathway for the formation of [MsH]+. The substitution ion from 1 and 2 and the [MH]+ ion from trans-1-amino-2-hydroxybenzosuberan give similar collision-induced dissociation mass-analysed ion kinetic energy spectra. Interestingly, their diacetates do not undergo the substitution reaction. 相似文献
Life-threatening diseases, especially those caused by pathogens and harmful ultraviolet radiation (UV-R), have triggered increasing demands for comfortable, antimicrobial, and UV-R protective clothing with a long service life. However, developing such textiles with exceptional wash durability is still challenging. Herein, we demonstrate how to fabricate wash durable multifunctional cotton textiles by growing in situ ZnO-TiO2 hybrid nanocrystals (NCs) on the surface of cellulosic fabrics. The ZnO-TiO2 hybrid NCs presented high functional efficiency, owing to their high charge transfer/separation. Ultrafine fiber surface pores, utilized as nucleating sites, endowed the uniform growth of NCs and their physical locking. The resulting fabrics presented excellent UV protection factors up to 54, displayed bactericidal efficiency of 100% against Staphylococcus aureus and Escherichia coli, and optimum self-cleaning efficacy. Moreover, the functionalized textiles exhibited robust washing durability, maintaining antibacterial and anti-UV-R efficiency even after 30 extensive washing cycles.
An ion-exchange approach to the preparation of chelating resin is demonstrated whereby a typical sulfonated chelating agent, 7-iodo-8-hydroxy quinoline-5-sulfonic acid, is immobilized as counterions on a piperazinium polyelectrolyte matrix. The resulting chelate forming resin has been used to effect the selective separation of ferrous as well as ferric ion from a known mixture containing other trace elements without any complication of the leaching of either chelating ligand or resin from the stationary support. The chelating resin-impregnated paper chromatographic technique followed with differential pulse anodic stripping analysis is described for the preconcentration, separation, and recovery of divalent and trivalent ions of iron from the various heavy metals in aqueous phases. The combination of chelation and paper chromatography involves a differential migration procedure which provides a technique for the separation of analyte ions quantitatively without any interference from the complex matrices. 相似文献
We have reported herein the synthesis of three new Cu(II) complexes of tri- and tetradentate Schiff base ligands containing
N3 or N4 donor set along with terminal NNN− or SCN− ligands: [L1Cu(NCS)]ClO4 (1), [L2Cu(NCS)2] (2) and [L3Cu(NNN)]ClO4 (3) [L1 = NC5H4C(CH3)=N(CH2)3N=C(CH3)C5H4N, L2= Me2N–(CH2)3–N=C(CH3)C5H4N and L3 = NC5H4CH=N–(CH2)4–N=CHC5H4N]. The complexes have been systematically characterised by elemental, spectroscopic and electrochemical techniques. Antimicrobial
activities of the Schiff base ligands and their metal complexes have been studied using the disc diffusion method on the strains
of Candida tropicalis and Bacillus megaterium. Structures of all the complexes have been unequivocally established from single crystal X-ray diffraction analyses that
show the monomeric units containing a five-coordinated copper center in highly distorted square pyramidal geometry with thiocyanate
or azide anion coordinated as terminal ligand. The complexes 1 and 3 crystallise in monoclinic (P21/c) and 2 in triclinic (P-1) space group, respectively. 相似文献
Diphasic Al2O3-SiO2 gels have been synthesized by hydrolyzing ethyl orthosilicate at three different pH ranges in presence of colloidal boehmite. Result shows that dominant mullitization process are sensitive to pH of the gelation process. At highly acidic pH range, solid state reaction between corundum and cristobalite occurs, and develops liquid phase for mullite nucleation. At moderately acidic pH, nucleation and crystallization are most operative for nucleation in aluminosilicate matrix. In highly basic pH region, Al-Si spinel phase develops by incorporation of Si in aluminous phase as intermediary phase. Polymorphic transformation of it may be the cause of sudden mullitization. The changes in crystallization sequence in three distinct processes may be due to variation in the nature and size of silicic acid particle formed by hydrolysis and condensation of TEOS at different pH. 相似文献