Determination of mercaptopyrimidines with copper(II) in acetonitrile

A non-aqueous oxidimetric method is described for the determination of mercaptopyrimidines with copper(II) perchlorate in acetonitrile, diphenylamine being used as indicator. A bright platinum wire is used as indicator electrode and a modified calomel or an antimony electrode as reference for potentiometric titrations. The method, based on the oxidation of the mercapto group to the disulphide, is simple, accurate and reliable.     

Volumetric studies in oxidation-reduction reactions: Oxidation with chloramine-t. indirect determinations

Chloramine-T has been used as an oxidizing agent in hydrochloric acid medium for the indirect volumetric determination of hydrogen peroxide, lead dioxide, selenium dioxide, sodium formate, potassium meta-periodate, potassium permanganate and potassium dichromate using iodine monochloride as a catalyst, prcoxidizer and an indicator. Chloroform is coloured pink owing to the liberation of iodine during the titration and becomes very pale yellow at the end-point because of the formation of iodine monochloride.     

Low-lying two-particle states in the nucleus236Np

The ambiguities and the uncertainties about the energy levels of the doubly odd actinide nucleus ₉₃ ²³⁶ Np₁₄₃ are sought to be removed by determination of the bandhead energies of various two-particle configurations expected to appear in the low energy spectrum of this nucleus. The calculations involve quantitative evaluation of the zero range neutron-proton residual interaction energy contribution to the bandhead energy for each configuration. It is concluded that the ground state is the long-lived isomer with spin-parityI ^π=6^- arising from the configuration {5/2⁺[642] _p +7/2^?[743] _n }. Bandhead energies for eight two-particle states appearing upto an excitation energy of 400 keV are presented and the results are discussed in the context of the available and further experiments.     

NMR studies of mixed cationic surfactants with similar tails and dissimilar bulky head groups

The mixed micelle formation by benzyldimethylhexadecylammonium chloride (BHDACl) with hexadecyltrimethylammonium bromide (HTAB), hexadecylpyridinium bromide (HPyBr), and hexadecylpyridinium choride (HPyCl) has been studied with the help of ¹H and ¹³C NMR studies influenced by both the head-group modifications as well as mutual hydrophobicity. The results showed that the mixed micelles of BHDACl+HPyBr and BHDACl+HPyCl mixtures are significantly affected by the steric factors originating from the bulkiness of the pyridinium head group of both cosurfactants in the stern layer. The result is that BHDACl+HPyBr and BHDACl+HPyCl mixed micelles are in the state of loose micellar arrangements rather than the mixed micelles of the BHDACl+HTAB mixture. A relative comparison between Br ^- and Cl ^- counterion effect suggests that the stronger binding ability of Br ^- than Cl ^-produces relatively compact mixed micelles.     

A simple and rapid spectrophotometric method for determination of thiophanate-methyl in commercial formulations and its residues in foodstuffs

A new, simple, rapid, and sensitive spectrophotometric method for the determination of thiophanate-methyl, based on its reaction with cobalt(II) in the presence of triethylamine, has been developed. The yellowish green color that develops instantaneously on mixing the fungicide with the reagents in dimethylformamide is stable for at least 2 h and has maximum absorbance at 360 nm. The method has been successfully applied to the determination of thiophanate-methyl in its commercial formulations and residues on grains and apples. A photometric titration procedure for formulation analysis of the fungicide has also been developed.     

Grafting onto polypropylene. I. Effect of solvents in gamma radiation-induced graft copolymerization of poly(acrylonitrile)

Graft copolymerization of acrylonitrile (AN) onto isotactic polypropylene (PP) fiber has been studied by using gamma rays from a 2100 Ci ⁶⁰Co source as initiator by preirradiation technique. The preirradiated PP was treated with AN and the mixture was graft copolymerized by heating to 100°C for different time periods. The percentage of grafting is determined as a function of total dose, reaction time, and monomer concentration. The effect of different solvents such as H₂O, CH₃OH, and dioxane upon percentage of grafting has been studied. The maximum effect was observed in water and the minimum in CH₃OH. PP—g—PAN was characterized by IR spectroscopic and thermogravimetric methods. A plausible mechanism of gamma radiation induced grafting of AN onto PP in the absence and in the presence of solvents has been proposed. An attempt has been made to compare the relative abilities of different solvents to influence grafting.     

Characterization of aliphatic and aromatic polyester hyperbranched dendrimers by AFM imaging

The aggregates of aliphatic (AL-PE) and aromatic polyester (AR-PE) hyperbranched dendrimers were imaged by tapping mode atomic force microscopy (AFM). The second and third generations of AL-PE dendrimers were adsorbed on mica in large aggregates of 150- and 166-nm diameters with little heights (ca. 1–2 nm). The origin of such flattened aggregates is attributed to their favorable adsorption on mica in view of the presence of –OH surface groups. AR-PE did not show such flattened aggregates instead small aggregates of 63 nm were observed in an organized manner beaving a cavity in the center of each aggregate. The organized aggregates of AR-PE with smaller dimension than AL-PE are ascribed to less favorable adsorption of the latter on mica in view of its stronger hydrophobicity.     

Bis(2,4–pentanedionato)vanadium(IV) aryloxides

Complexes of composition [VCl(acac)2(OAr1–4)] and [V(acac)2(OAr1–4)2] (HOAr1=HOC6H4NO2–4, HOAr2= HOC6H4OMe-4, HOAr3=HOC6H4But-4 and HOAr4= HOC6H2But-2,6–Me-4; acac=2,4–pentanedionato ion) have been synthesized by the reaction of [VCl2(acac)2] with the respective phenols or their trimethylsilyl derivatives. The complexes have been characterized by physicochemical and spectroscopic techniques. They are non-electrolytes in nitrobenzene. Room temperature magnetic moments in the 1.71–1.82B range are consistent with the VIV system. The reactions of [VCl(acac)2(OAr2)] and [VCl(acac)2(OAr3)] with chloride acceptors have been studied by conductance techniques and the formation of ionic complexes of the types [V(acac)2(OAr2,3)][MCl4] (M=Fe, Al or Sb) and [V(acac)2(OAr2,3)][MCl6] (M=P or Sb) is indicated by the conductance composition curves. Several of these complexes have been isolated and characterized.     

Non-aqueous cerimetric determination of phenylhydrazides

A non-aqueous oxidimetric method is described for the determination of some carboxylic acid phenylhydrazides with ammonium hexanitratocerate(IV) in acetonitrile. The end-points have been detected visually with chemical indicators (diphenylamine, diphenylbenzidine, Methyl Red, Malachite Green, Janus Green, Gentian Violet) and potentiometrically. The compounds are smoothly, rapidly and quantitatively oxidized with a two-electron change per hydrazino group. The method is simple, accurate, reliable and widely applicable.     

Thermal decomposition of nickel azide

The results on the thermal decomposition of anhydrous nickel azide prepared by reacting nickel azide solution with AnalaR Me₂CO are reported in the temperature range 490–525 K. The sample starts to decompose immediately after it is raised to the decomposition temperature and the rate of decomposition continuously decreases. The decomposition kinetics have been explained in terms of exponential decay law for α?0.19 and contracting volume law for α > 0.19. The domain of exponential decay law corresponds to the initial decomposition pertaining to surface nucleation and two dimensional surface growth of the product phase, while contracting volume law explains the growth of the product phase into the bulk. The role of defects has been explained by electrical conduction studies on the sample.