NOPR Collection:

Refractometric and dielectric studies of binary liquid mixtures at different temperatures

Wed, 01 Mar 2006 00:00:00 GMT

Title: Refractometric and dielectric studies of binary liquid mixtures at different temperatures Authors: Pandey, J D; Chhabra, Jyotsna; Soni, N K; Tiwari, K K; Mishra, R K Abstract: Thermal expansion coefficients of binary mixtures, viz...methyl acetoacetate + aliphatic alcohols (C₃-C₈) at different temperatures, 298.15 K, 303.15 K and 308.15 K, have been computed theoretically using Eykman and Lorentz- Lorenz Reelation, and are compared with experimental findings. Deviations in refractive indices, dielectric constant and molar polarization have been computed for six binary mixtures. viz... 1,2-dichloroethane + n-alkanes/2,2,4-trimethylpentane at two temperatures, 293.15 K and 313.15 K. Computed properties have been utilized to study the molecular interactions occurring in mixtures. Page(s): 653-656

Quantification of Bronsted acidity of rare earth exchanged (Ce³⁺, La³⁺, Sm³⁺and RE³⁺) NaFAU-Y zeolites in their Bronsted acid forms

Wed, 01 Mar 2006 00:00:00 GMT

Title: Quantification of Bronsted acidity of rare earth exchanged (Ce³⁺, La³⁺, Sm³⁺and RE³⁺) NaFAU-Y zeolites in their Bronsted acid forms Authors: Thomas, Bejoy; Sugunan, S Abstract: Thermodesorption of sterically hindered molecule such as 2,6- dimethyl pyridine (2 ,6-DMP) and cumene cracking test reactions have been applied to determine the nature of Bronsted acid sites (BAS) in pure H-Y, and various rare earth exchanged (Ce³⁺, La³⁺, Sm³⁺and RE³⁺) Na-Y zeolites. Incompatibility in the amount of 2.6-DMP desorbed is clearly an indication of the influence of the nature of rare earth metal ions in producing BAS in zeolites. A one- to-one correlation has been observed between the amount of benzene formed during the catalytic cracking of cumene and Bronsted acidity measured by thermodesorption of the probe molecule. Page(s): 648-652

Cyclic voltammetry of Ga(III) in sodium perchlorate and sodium thiocyanate at static mercury drop electrode

Wed, 01 Mar 2006 00:00:00 GMT

Title: Cyclic voltammetry of Ga(III) in sodium perchlorate and sodium thiocyanate at static mercury drop electrode Authors: Sharma, H S; Bhardwaj, T K; Jain, P C; Aggarwal, S K Abstract: Cyclic voltammetry (CV) of Ga(III)/Ga electrode process has been investigated in sodium perchlorate as well as in sodium perchlorate containing sodium thiocyanate, at Static Mercury Drop Electrode (SMDE). Large difference between cathodic and anodic peak potentials (ΔE ≈600 mV) and ratio of anodic to cathodic peak current (I_pc/I_pa ≈0.1) confirm that the electrode process involving electro- reduction of Ga(III ) and electrooxidation of Ga is highly irreversible at SMDE. Effect of concentrations of sodium perchlorate, sodium thiocyanate and scan rate on the CV behaviour has also been studied. The Ga(III)/Ga electrode process remains highly irreversible in 1-4 M sodium perchlorate. However, positive shift of ≈480 mV in cathodic peak potential is observed on adding 0.5 M sodium thiocyanate to sodium perchlorate and the CV behaviour approaches closer to reversible in 4 M NaClO₄+O.5 M NaSCN. Maximum anodic and cathodic peak currents of unequal heights are observed at 0.5 M sodium thiocyanate in 4 M sodium perchlorate. The electrode processes of Ga(III) reduction has been found to be diffusion controlled in 3-4 M NaClO₄ in presence of 0.5 M NaSCN and electro-oxidation in 2-4 M NaClO₄ in presence or 0.5 M sodium thiocyanate. Controlled potential coulometry confirms that Ga(III)/Ga electrode process involves three electron transfer and electro-oxidation of Ga to Ga (III) is much faster as compared to electro-reduction of Ga (III) in 4 M NaClO₄+0.5 M NaSCN. Page(s): 643-647

Mercury(II) ion sensing with PVC-matrix based membrane sensors

Wed, 01 Mar 2006 00:00:00 GMT

Title: Mercury(II) ion sensing with PVC-matrix based membrane sensors Authors: Mahajan, Rakesh Kumar; Kaur, Ravneet; Lobana, Tarlok S Abstract: Thiosemicarbazone derivatives have been used as ion carriers for the preparation of PVC-matrix based mercury(II)selective membrane sensors. The electrodes give near-Nernstian responses in the linear concentration range of 1.0×10^-1-5.0×10^-6 M with detection limits of the order of ~10^-6 M . The stable potentiometric signals are obtained within a short time period of 20-255. The effect of different plasticizers has been studied and dioctylsebacate (DOS) found to give a better response in comparison to other plasticizers. Selectivity coefficient values (log K^Pot_Hg,_M ) have been evaluated using fixed interference method. Better selectivity for mercury(II) ions is observed over many of the mo novalent (Na⁺, K⁺ and NH₄⁺) and divalent ions (Mg²⁺, Ca²⁺, Zn ²⁺ , Pb²⁺ , Ni²⁺, Co²⁺, etc.). The sensors have also been used as indicator electrodes in potentiometric titration of mercury(II) ions with EDT A and its determination in synthetic water samples. Page(s): 639-642

NOPR Collection:

Refractometric and dielectric studies of binary liquid mixtures at different temperatures

Quantification of Bronsted acidity of rare earth exchanged (Ce3+, La3+, Sm3+and RE3+) NaFAU-Y zeolites in their Bronsted acid forms

Cyclic voltammetry of Ga(III) in sodium perchlorate and sodium thiocyanate at static mercury drop electrode

Mercury(II) ion sensing with PVC-matrix based membrane sensors

Quantification of Bronsted acidity of rare earth exchanged (Ce³⁺, La³⁺, Sm³⁺and RE³⁺) NaFAU-Y zeolites in their Bronsted acid forms