Polyaromatic hydrocarbon profile of a mineral oil (JBO-P) by gas chromatography

The present investigation was aimed at identifying the compound(s) responsible for the carcinogenic activity of a variety of jute batching oil (known as non-FDA variety, pre-FDA variety, or JBO-P), a crude petroleum distillate substantially used in jute industries. This was initially performed by isolating from JBO-P a polyaromatic hydrocarbon (PAH) fraction containing compounds of more than three rings. This fraction was then analysed for its PAH profile by gas chromatography and individual components identified by comparing its flame ionisation detector (FID) signal with those obtained from reference PAHs. The results revealed that PAHs of more than three rings, reported to be a recognised class of chemical carcinogens, were present in the JBO-P sample at the level of 3300 mg/kg of oil (0.33%, w/w); benzo(a)pyrene and dibenz(a,h)anthracene, known to be highly potent carcinogens, constituted 129 mg/kg (0.0129%, w/w) and 29 mg/kg (0.0029%, w/w) of the total oil, respectively; and except for a few signals, the PAH profile of JBO-P was found to be somewhat similar to that reported for a sample of carcinogenic used engine oil.     

Congo red as adsorption indicator

1. A new adsorption indicator 'Congo red' has been described for argentometric titraitions. 2. The new indicator differs from all those described earlier in having both acidic as well as basic character, on account of which it is adsorbed with different colours, by both the positively and negatively charged halide bodies. 3. The adsorbability of the indicator by both the positively as well as the negatively charged halide bodies, endows it with a sharp colour change at the end point, a ready reversibility and a large range of applicability in the argentometric titrations. 4. The great usefulness of the indicator lies in its being applicable both in the titrations of halide ions by silver ions and also in the reverse estimations of silver ions by halide solutions. 5. The end point is particularly sharp as the colour change occurs from one end of the spectrum to the other: blue to red and vice versa. 6. The effect of the addition of a protective colloid 'dextrin' has been found to make the end points even sharper.     

Temperature dependent dielectric relaxation study of ethylene glycol-water mixtures

Using the picosecond time domain reflectometry method, dielectric relaxation measurements for 13 ethylene glycol (EG)-water mixtures have been studied from 0 to 40°C. The dielectric relaxations in the mixtures show a Debye-type behavior, whereas the relaxation in pure EG can be described by the Cole-Cole model. The static dielectric constant ₀, the relaxation time and the dielectric constant at high frequency have also been determined at various temperatures. The dielectric relaxation data suggests that there is no tendency to form hydrogen bonds with the addition of water to EG unlike other alcoholic systems but this tendency becomes increasingly important with decreasing temperature. The activation energy decreases with increased water content in the mixture as expected.     

Spectrophotometric method for estimation of alkaloids precipitable with Dragendorff's reagent in plant materials

A rapid, easy, and simple spectrophotometric method was developed for the estimation of total alkaloids precipitated by Dragendorff's reagent (DR) in plant materials. It is based on the formation of yellow bismuth complex in nitric acid medium with thiourea. The yellow-colored complex formed obeys Lambert-Beer's law in the concentration range of 0.06-50 microg/mL with lambdamax at 435 nm. Using this method, the alkaloidal percentage of certain alkaloids (ajamalicine, papaverine, cinchonine, piperine, berberine) and some plant materials containing alkaloids (Berberis aristata, Solanum nigrum, and Piper longum) were determined. The method was compared with other methods. It can be used for routine analysis of commercial samples by industries dealing with herbal drugs for standardization of plant materials containing alkaloids and for alkaloid-containing pharmaceutical products.     

Complex Permittivity Spectra of Binary Pyridine–Amide Mixtures Using Time–Domain Reflectometry

Frequency spectra of the complex permittivity for pyridine–amide binary mixtures have been determined over the frequency range 10 MHz to 10 GHz, at 5, 15, 25, and 40°C, using the time–domain reflectometry method, for 11 compositions of each pyridine–amide system, e.g., formamide, N-methylformamide, and N,N-dimethylformamide. The relaxation in these systems can be described by a single relaxation time using the Debye model. The static dielectric constant, relaxation time, the corresponding excess dielectric properties, Kirkwood correlation factor, and molar activation energy of the mixtures have been determined. The excess permittivity is found to be positive in the amide-rich region and negative in the pyridine-rich region. The excess inverse relaxation time is negative, except in the pyridine-rich region. The static dielectric constants for the mixtures have been fitted with the modified Bruggeman model. The temperature-dependent relaxation times show the expected Arrhenius behavior.     

O,O′-Alkylene dithiophosphate derivatives of iron(II) and iron(III) and their reactions with nitrogen- and phosphorus-donor bases

Summary Solids of the stoichiometric formulae [Fe{S₂P(OPr-n)₂}₃] and [Fe{S₂PO₂G}₃] (G = —CH₂CMe₂CH₂—, CMe_2–CMe₂— or —CH₂CH₂CHMe—) are precipitated from the reactions of FeCl₃ with ammonium dithiophosphates in water. Soluble complexes of the type [Fe{S₂PO₂G}₂], formed by the reactions of FeCl₂ with NH₄[{S₂PO₂G}] in MeOH, can be extracted with benzene. Adducts of the types [Fe{S₂PO₂G}₂L] and [Fe{S₂PO₂G}₂(PPh₃)₂] are formed by the reaction of [Fe{S₂PO₂G}₂] with L (L = 2,2-bipyridyl or 1,10-phenanthroline) and PPh₃, respectively. All the compounds have been characterized by i.r. and u.v.-vis. spectroscopy and magnetic studies.This paper is dedicated to the late Dr. G. Srivastava, Associate Professor, Department of Chemistry, Rajasthan University, Jaipur.     

Nanoparticles in solutions of adsorbing polymers: pair interactions, percolation, and phase behavior

We study the polymer adsorption characteristics, pair-interaction potentials, and phase and percolation behavior in nanoparticle-polymer mixtures. We propose a "saturable" adsorption model to capture the effect of the finite surface saturation capacity for adsorption, and use polymer self-consistent field theory in combination with a McMillan-Mayer framework [McMillan, W. G., Jr.; Mayer, J. E. J. Chem. Phys. 1945, 13, 276] to compute the pair-interaction potentials. Our results demonstrate novel size effects that distinguish the adsorption characteristics of nanoparticles from that of larger particles. Specifically, we predict that the nanoparticle regime is characterized by a significant adsorbance of polymers, albeit distributed predominantly in the form of tails. We also demonstrate that an interplay between the surface saturation, polymer-to-particle size ratios, and the polymer concentrations governs the overall effective interactions between nanoparticles in the presence of an adsorbing polymer. We use simple, mean-field models to relate these characteristics to the phase and percolation behavior in such systems. Our results show that the percolation thresholds for smaller particles are significantly smaller (and, overall, correspond only to a few volume percent) compared to that of the larger particles. Further, with a decrease in the size of the particles, we also predict a considerable increase in the miscibility of the polymer-particle mixtures. Our results are qualitatively in accord with many experimental observations in the nanoparticle regime.     

Arithmetic approach for complex PSA cycle scheduling

An algebraic model was derived for obtaining complex pressure swing adsorption (PSA) cycle schedules. This new approach involves a priori specifying the cycle steps, their sequence and any constraints, and then solving a set of analytical equations. The solution identifies all the cycle schedules for a given number of beds, the minimum number of beds required to operate the specified cycle step sequence, the minimum number and location of idle steps to ensure alignment of coupled cycle steps, and a simple screening technique to aid in identifying the best performing cycles that deserve further examination. The methodology was tested successfully against 10, 12 and 16 bed PSA systems in the literature that all utilized the same 13 step cycle sequence that has four pressure equalization steps. It completely resolved all the corresponding cycle schedules for these 13 step multi-bed PSA systems with ease, and showed that the number of cycle schedules was hundreds to thousands of times greater than the few ever reported in the literature for each one. Overall, this new methodology for complex PSA cycle scheduling can be applied to any number of cycle steps, any corresponding cycle step sequence, and any number of constraints, with the outcome being the complete set of cycle schedules for any number of beds greater than or equal to the minimum number it determines.     

Molecular Design of Novel Heterometallic Alkoxides as Precursors

In view of the advantages of employing heterometallic alkoxides as precursors for ceramic materials by the sol-gel process, efforts are being made to develop novel routes for their synthesis and to design single source precursors suited to the final targeted material. Three such new pathways are briefly presented in this paper: (i) varying the ratio of constituent metals; (ii) dissolution of metal chlorides in alkoxides of tetravalent metals; and (iii) reactions of acidic protons of metal glycolate derivatives with alkoxides of another metal yielding derivatives containing other alkoxometallates in cationic form.