DMSO Mixtures Research Articles

Crystallization dynamics of MAPbI3 perovskite solar cells via solvent engineering methods

Perovskite materials have attracted interest in solar cells due to ease of processing from salts. However, the complex crystal formation of perovskite from solvents is poorly understood. Solvent engineering approach to determine the crystallization dynamics and orientation of MAPbI3 films using grazing incidence wide angle x-ray scattering (GIWAXS) and micro diffraction measurements were studied. The study further probes the effect of moisture, PTAA and PEDOTS: PSS hole transport layers on the stability of MAPbI3 films. Precursor solutions were prepared by dissolving MAI and PbI2 in pure DMF and mixture of DMF: DMSO in 4:1 v/v. Chlorobenzene and Ethyl acetate were used as antisolvent. Films prepared from DMF: DMSO mixture showed no PbI2 signature while those prepared from DMF only, showed PbI2 signature at q= 0.9 A-1. This was attributed to solvent engineering of DMF/DMSO that leads to the formation of MAI/PbI2/DMSO intermediate that delays the crystallization and promotes vertical growth of films. q= 0.9 A-1 signal was associated with high volatility of DMF which led to faster but discrepant nucleation and crystallization rate. Microdiffraction results showed insignificant influence of antisolvent on the perovskite structure. Humidity has a strong influence on the stability of MAPbI3 films. PbI2 intensity in the GIWAXS maps increased with increasing humidity while MAPbI3 intensity decreased. This implied increased degradation of MAPbI3 film with humidity due to recombination of charge carriers. A band gap of 1.57 eV, efficiency of 8.5% and Et of 26 meV were obtained. Films with good crystallization are desirable in solar cells.

Reducing the danger of phytopathogen toxins by using an organomineral composition

Relevance. Contamination by toxins of phytopathogens or mycotoxins of food and feed raw materials of plant origin poses a serious threat to the production of high-quality and safe agricultural products. Reducing the risks of contamination of plant raw materials with mycotoxins depends on the effective use of biological products to reduce the toxicity of mycotoxins.Methods. Experiments were carried out on primary rat liver cells. Primary liver cells were cultured in DMEM medium in the presence of 10% fetal calf serum at 37OC and 5% CO2. Zearalenone and T-2 toxin were dissolved in a mixture of DMSO and 96% alcohol in a ratio 1:1. Zearalenone T-2 toxin and protective compositions were mixed and aged together for 6 hours and after exposure added to a medium with a cellular monolayer. The concentration of bacterial-based compositions KMBI-3 and KMCI-3 was used for research in three variants: 0.4 mg/ml, 2 mg/ml, 4 mg/ml. After 24 hours of cultivation, the cell layer was evaluated using an inverted microscope according to the following parameters: percentage of surface coverage, cell shape, number of cell aggregates, number of floating cells.Results. A dose-dependent decrease in cell viability was revealed when exposed to zearalenone and T-2 toxin, the most toxic effect was observed at doses from 0.5 х 10-4 and 8.6 х 10-8 M and 2.14 х 10-7 M, respectively. When using the protective composition KMBI-3 at a dose of 4 mg/ml, the least negative effect of zearalenone and T-2 toxin on cell culture was observed. The use of compositions of organomineral origin KMBI-3 helps to increase cell viability when exposed to the toxins zearalenone and T-2 toxin, which indicates the activation of proliferative processes in comparison with the group without the use of drugs. The use of the biopreparation KMBI-3 reduces the pathogenic effect of zearalenone and T-2 toxin on cell culture, increases the resistance of liver cells to the effects of phytopathogen toxins.

Synthesis of BODIPY-pyrrolo[3,4-b]pyridin-5-ones via Ugi-Zhu/cascade reactions and studies of fluorescence response toward viscosity.

A series of seven new meso-phenyl BODIPY-pyrrolo[3,4-b]pyridin-5-one conjugates were synthesized in one experimental step by using a Sc(III)-catalyzed Ugi-Zhu three-component reaction coupled to a cascade sequence (aza Diels-Alder/N-acylation/aromatization) as post-MCR functionalization process. Further experimental studies were performed behind understanding the fluorescence response toward viscosity. All compounds exhibited a linear response between increasing viscosity (DMSO and glycerol mixtures) and fluorescence intensity. The different substituents also influenced the photophysical properties. Furthermore, in DMSO all compounds exhibited dual emission. Each band is attributed to the pyrrolo[3,4-b]pyridin-5-one and BODIPY moieties, respectively. The electronic structure of all compounds was computed by DFT and TD-DFT calculations, allowing to determine the molecular orbitals involved in the electronic transitions.

SYNTHESIS OF NEW FRAMEWORK PHOSPHONATES BY THE INTERACTION OF 2-ETHOXYVINYL DICHLOROPHOSPHONATE WITH 4-ETHYLRESORCINOL

A simple, new and promising approach to obtaining previously unknown phosphorus-containing framework compounds by the developed original synthesis method is proposed. The proposed method is based on the condensation reaction of 2-ethoxyvinylphosphonic acid dichloride with resorcinol and its derivatives in toluene in the presence of trifluoroacetic acid. The article presents the results of a study of the reaction of 2-ethoxyvinyl dichlorophosphonate with 4-ethylresorcinol. It was found that this reaction results in the formation of a mixture of two regioisomers. The structure and construction of the obtained regioisomeric framework phosphonates were studied using 31P and 1H NMR. The regioisomeric framework phosphonates obtained as a result of the reaction of vinylphosphonate with 4-ethylresorcinol were separated by acylation of the mixture with acetic anhydride, using as a medium and a reagent. One functionalized regioisomer was isolated as an individual product, which was white crystals with good solubility in acetone-water and DMSO mixtures. The structure and composition of the obtained regioisomer were confirmed by 1H, 31P, 13C NMR, IR spectroscopy, mass spectrometry (MALDI) and elemental analysis. It was found that the reaction of 2-ethoxyvinyl dichlorophosphonate with 4-ethylresorcinol in the presence of an equimolar amount of trifluoroacetic acid in toluene resulted in the formation of a regioisomeric mixture of framework phosphonates in a 4:1 ratio. It was shown that acylation of this regioisomeric mixture with acetic anhydride allowed one of the regioisomers to be isolated individually.

Selective extraction of Quercetin from rose petal extracts using poly (acrylamide-co-ethylene glycol dimethylacrylate) based magnetic molecularly imprinted polymer

Under ultrasound irradiation, a highly selective Magnetic Molecularly Imprinted Polymer (MMIP) was synthesized by polymerizing monomers on magnetite. The Density Functional Theory was utilized for the selection of suitable monomers based on binding energy interaction between quercetin and monomers (Acrylamide, Acrylonitrile, Methacrylic Acid). Quercetin served as the template molecule, while acrylamide was used as the functional monomer, and a mixture of DMSO and water was employed as the porogen solvent. This study aims to synthesize and evaluate the effectiveness of MMIP and analyze its adsorption isotherm and kinetics. It was observed that the Freundlich model supports the adsorption of quercetin on MMIP, and the kinetic data correlates better with the Pseudo-first-order kinetic model. The MMIP exhibited a pronounced selectivity in the adsorption of quercetin with a maximum adsorption capacity of 10.07 mg g-1 in 30 min. Furthermore, the physiochemical properties of synthesized sorbent were undergone for characterization using FESEM, EDX, XRD, FTIR, VSM, and TGA. Finally, real-time determination of quercetin was carried out using rose petal extract, integrating MMIP adsorption followed by HPLC detection. The results suggest that MMIP is a promising material for the real-time determination of quercetin from rose petal extract.

(Invited) Controlling Electric Fields and Hydration at Electrochemical Junctions Using Surfactants

Tuning the electrostatics and the water structure at the nm and sub-nm scales are two important frontiers towards the broader goal of controlling reactivity at interfaces. Surfactants offer a way to influence both the electrostatics and hydration of an electrochemical interface. Here we report measurements of local electric fields generated between layers of surfactants and an electrode without application of an external potential. We estimate the value of the electric field by measuring the vibrational frequency shift of a well-defined Stark probe that is adsorbed on the electrode. The field generated by the common quaternary ammonium surfactants in aqueous media is estimated to be in the order of 1 V/nm. We show that modest quantities of surfactants (50 mM) can produce polarizing fields similar to those produced by an electrode poised at -0.8 V vs. Ag/AgCl. Furthermore, we show that under electrochemical conditions, surfactants offer a way of modulating the water content near the electrode. In a mixture of water and DMSO, there are two forces that act upon the surfactants to drive them to the interface: they hydrophobic forces and the electrostatic forces from the electrode. We measure the surfactants at the interface as a function of these variables using surface enhanced IR spectroscopy, and arrive at quantitative comparisons between these two effects. These results help in understanding the design principles of modifying interfacial reactions via tailored surfactants.

New Methodology for Modifying Sodium Montmorillonite Using DMSO and Ethyl Alcohol.

Modified clays with organic molecules have many applications, such as the adsorption of pollutants, catalysts, and drug delivery systems. Different methodologies for intercalating these structures with organic moieties can be found in the literature with many purposes. In this paper, a new methodology of modifying Sodium Montmorillonite clays (Na-Mt) with a faster drying time was investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), BET, and thermogravimetric analysis (TG and DTG). In the modification process, a mixture of ethyl alcohol, DMSO, and Na-Mt were kept under magnetic stirring for one hour. Statistical analysis was applied to evaluate the effects of the amount of DMSO, temperature, and sonication time on the modified clay (DMSO-SMAT) using a 23-factorial design. XRD and FTIR analyses showed the DMSO intercalation into sodium montmorillonite Argel-T (SMAT). An average increase of 0.57 nm for the interplanar distance was found after swelling with DMSO intercalation. BET analysis revealed a decrease in the surface area (from 41.8933 m2/g to 2.1572 m2/g) of Na-Mt when modified with DMSO. The porosity increased from 1.74 (SMAT) to 1.87 nm (DMSO-SMAT) after the application of the methodology. Thermal analysis showed a thermal stability for the DMSO-SMAT material, and this was used to calculate the DMSO-SMAT formula of Na[Al5Mg]Si12O30(OH)6 · 0.54 DMSO. Statistical analysis showed that only the effect of the amount of DMSO was significant for increasing the interlayer space of DMSO-SMAT. In addition, at room temperature, the drying time of the sample using this methodology was 30 min.

Low-Temperature Mineralization of Fluorotelomers with Diverse Polar Head Groups.

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental pollutants linked to harmful health effects. Currently employed PFAS destruction methods are energy-intensive and often produce shorter-chain and recalcitrant partially fluorinated byproducts. We report the mineralization of five fluorotelomer compounds via a base-mediated degradation using NaOH and mild temperatures (120 °C) in a mixture of DMSO:H2O (8:1 v/v). The studied fluorotelomers have varying polar head groups-carboxylic acids, sulfonic acids, alcohols, and phosphonic acids, which are the most common polar head groups used in commercial and industrial applications. The degradation intermediates and byproducts were characterized using 1H, 13C, and 19F NMR spectroscopy. Density functional theory computations at the M06-2X/6-311 + G(2d,p)-SMD-(DMSO) level were consistent with the observed intermediates and guided an overall mechanistic hypothesis. Degradation of each fluorotelomer occurs through a similar process, in which the nonfluorinated carbons and the first fluorinated carbon are cleaved from the remaining perfluoroalkyl fragment, which degrades through previously identified pathways. These findings provide important insight into PFAS degradation processes and suggest that PFAS containing at least one C-H bond within or adjacent to its fluoroalkyl chain can be degraded under these mild conditions. Many PFAS in current use as well as recalcitrant fluorinated byproducts generated from other PFAS degradation methods are candidates for this approach.

A Siderophore Mimicking Gelation Component for Capturing and Self-Separation of Fe(III) from an Aqueous Solution of Mixture of Metal Ions.

The carbohydrazide-based gelation component N2,N4,N6-(1,3,5-triazine-2,4,6-triyl)tris(benzene-1,3,5-tricarbohydrazide) (CBTC) was synthesized and characterized using various spectroscopic tools. CBTC and trimesic acid (TMA) get self-assembled to form metallogel with Fe3+, specifically through various noncovalent interactions in a DMSO and H2O mixture. The self-assembly shows remarkable specificity toward Fe(III) among different transition metal salts. It is pertinent to point out that the binding specificity for Fe3+ can also be found in nature in the form of siderophores, as they are mainly involved in scavenging iron selectively from the surroundings. DFT studies have been used to investigate the possible interaction between the different components of the iron metallogel. To determine the selectivity of CBTC for iron, CBTC, along with trimesic acid, is used to interact with other metal ions, including Fe(III) ions, in a single system. The gelation components CBTC and TMA selectively bind with iron(III), which leads to the formation of metallogel and gets separated as a discrete layer, leaving the other metal ions in the solution. Therefore, CBTC and TMA together show iron-scavenging properties. This selective scavenging property is explored through FE-SEM, XPS, PXRD, IR, and ICP-AES analysis. The FE-SEM analysis shows a flower-petal-like morphology for the Fe(III) metallogel. The resemblance in the CBTC-TMA-Fe metallogel and metallogel obtained from the mixture of different metal salts is established through FE-SEM images and XPS analysis. The release of iron from the metallogel is achieved with the help of ascorbic acid, which converts Fe3+ to Fe2+. In biological systems, iron also gets released similarly from siderophores. This is the first report where the synthesized gelation component CBTC molecule is capable of scavenging out iron in the form of metallogel and self-separating from the aqueous mixture in the presence of various other metal ions.

Electrochemical Hydroxylation of α‐Bromoacetophenones: Access to α‐Hydroxyacetophenones

AbstractHerein, a new method has been developed for the synthesis of various α‐hydroxyacetophenones via an electro‐oxidation process. It involves electrocatalytic hydroxylation via debromination of C(sp3)−Br bond. Here, simultaneous breaking of carbon‐bromine (C−Br) bond and formation of a new carbon‐oxygen (C−O) bond has been achieved through electrolysis of H2O using binary mixture of water and DMSO. The protocol features easy performance, oxidant and base‐free mild conditions and short reaction time.

Design and synthesis of pyrene-based probes and their fluorescent detection of Sb(III)

A series of pyrene-based fluorescent (FL) probes for Sb(III) were designed and synthesized. All of them exhibited luminescence by pyrene excimers in the mixture of DMSO and water and showed enhanced emission with the addition of Sb(III). By comparing their FL response to Sb(III), the effects of intramolecular hydrogen bond, inductive effect, and steric effect were investigated. Meanwhile, the FL enhancement factor of the best performing probe reached 10.28 and the detection limit was calculated to be 0.0535 mg/L, indicating that it might be used as a potential candidate for the treatment of Sb(III) in printing and dyeing wastewater.

Liver and mucous secretion enzymatic biomarkers of Eobania vermiculata treated with some newly synthesized acrylamide derivatives

Abstract Background Acrylamide derivatives have a potential biological activity as well as acting as precursors in many organic syntheses. Moreover, acrylamides and their derivatives cause convulsions and diffused damage to different sections of the nervous system of infected animals. Novel copper and zinc chelates originated from (E)-3-(4-bromophenyl)-2-cyanoacrylamide (L1), and (E)-2-cyano-3-(4-nitrophenyl)acrylamide (L2) were prepared, and their chemical skeletons were identified by infrared and mass spectra. The obtained compounds were screened in vitro against the brown garden snail, Eobania vermiculata using the contact method along 72 h. Stock solutions of tested compounds were prepared utilizing distilled water and DMSO mixture, and four concentrations of each compound were prepared (50, 150, 250 and 350 ppm). Eobania vermiculata snails were treated with LC50 concentrations of prepared compounds for 3 days, and live snails were used to estimate the level of some liver and mucous secretion enzymatic biomarkers: transaminases enzymes (Alanine Aminotransferase (ALT) and Aspartate Aminotransferase (AST)), Total Protein content (TP), Acid Phosphatases (ACP) and Alkaline Phosphatase (ALP). Results The results demonstrated that the examined compounds have a relatively toxic effect toward the screened species. Zinc complexes displayed a higher toxicity than copper ones. The results authenticated considerable high effects of the synthesized compounds on investigated enzymes. Conclusions The promising effects of Cu(II), Zn(II) complexes (1, 2) on stimulating the mucous secretion of tested snails are clear through the elevated levels of ALP and ACP enzymes of treated snails. The enhancement or reduction of AST, ALT level and TP content of treated snails demonstrated the effects of prepared compounds on liver functions of these species.

Dielectric relaxation studies of 1-nitropropane-dimethyl sulfoxide mixtures using a Time Domain Reflectometry

ABSTRACT Complex dielectric measurements were performed in 1-nitropropane (NTP) and DMSO mixtures at various concentrations in the frequency range of 10 MHz to 50 GHz using time domain reflectometry technique. The excess inverse relaxation time values were found to be negative, indicating that the dipoles rotated more slowly. Alenka Luzar’s hydrogen-bonded theory is used to calculate theoretical estimates of the static dielectric constant. The variations in dielectric parameters such as dielectric constant, relaxation time, Kirkwood correlation factor and excess properties observed in the study confirm the existence of intermolecular interactions within the NTP-DMSO mixtures.

Exploring Non-aqueous Solutions for CO2 Capture at Elevated Pressure: An Initial Study for EHA/MOR in DMSO Mixtures

Exploring Non-aqueous Solutions for CO₂ Capture at Elevated Pressure: An Initial Study for EHA/MOR in DMSO Mixtures

An effective approach for chitosan conversion to 5-hydroxymethylfurfural catalyzed by bio-based organic acid with ionic liquids additive

The primary challenges associated with converting chitin biomass into 5-hydroxymethylfurfural (5-HMF) primarily revolve around achieving high 5-HMF yields while overcoming various limitations from traditional acid-based catalysts, including complex post-treatment procedures, by-product generation, and equipment corrosion. In this view, a novel approach was developed to synthesize 5-HMF from chitosan under hydrothermal process using a mixture of DMSO and water as reaction medium. Biomass-derived organic carboxylic acids were used as catalysts due to their weaker corrosiveness compared to mineral acids. The acidity of the bio-based acid was adjusted using inexpensive ionic liquids. By combining 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) with oxalic acid (OA), an excellent 29.1 % yield of 5-HMF conversion was achieved on the optimized condition. The improved dissociation ability of OA by [BMIM]Cl played a crucial role in this outcome. Using FTIR and density functional theory (DFT) techniques allowed for the proposal of a dissociation mechanism for OA induced by [BMIM]Cl, involving hydrogen bond interactions and the weakening of the O–H bond, facilitating the easy dissociation of hydrogen in the O–H group with H+ formation. Furthermore, the untreated chitosan and the solid residues obtained during the conversion process were characterized revealing the gradual conversion and the quaternization in the NH2 group of chitosan.

Optical Absorbance of Graphenic Carbon from Coconut Shells in Different Solvents for Film Preparation

Graphene-based materials have been widely developed in various applications, both in electronics and optoelectronics. It is because of their attractive characteristics, such as flexible structure, large surface area, and excellent thermal, mechanical, and optoelectronic properties. In this research, the optical absorbance of coconut shell-based carbon materials was studied in the exfoliation process and the type of solvent. To determine the effect of optical absorption and particle size of graphene carbon from coconut shells on solvents, we used two types of solvents, namely Deionized (DI) water and a mixture of DMSO and DI (DMSO/DI) with a fraction of 1:10. The exfoliation process is carried out by dissolving graphene powder from coconut shell powder that has been synthesized and heated at 400°C into DI water and DMSO/DI mixture with a concentration of 0.01 g/ml. Ultrasonication is carried out with time variations of 60, 180, 300, and 420 minutes. After ultrasonication for 420 minutes, the absorbance peak was at 241 nm with an average particle size of 134 nm in the solvent DMSO/DI mixture. For the DI solvent, the absorbance peak was at 243 nm with an average particle size of 198 nm. This study showed that the DMSO/DI mixed solvent with a fraction of 1:10 could produce a smaller average particle size than the DI solvent, but the absorbance spectrum is less clear at a wavelength of less than 240 nm compared to the DI water. Furthermore, these two solvents can be used to prepare graphenic carbon films from coconut shells because they are easy to obtain, cheap, and can reduce particle size by ultrasonication.

Effective Improvement of the Photovoltaic Performance of Lead-Free Perovskite Solar Cells Employing a Mixture of DMSO and Activated Carbon Powder as Counter Electrode: A Combined Experimental and DFT Study

Effective Improvement of the Photovoltaic Performance of Lead-Free Perovskite Solar Cells Employing a Mixture of DMSO and Activated Carbon Powder as Counter Electrode: A Combined Experimental and DFT Study

Antisolvent Crystallization of Telmisartan Using Stainless-Steel Micromixing Membrane Contactors.

Controlled continuous crystallization of the active pharmaceutical ingredient (API) telmisartan (TEL) has been conducted from TEL/DMSO solutions by antisolvent crystallization in deionized water using membrane micromixing contactors. The purpose of this work was to test stainless-steel membranes with ordered 10 μm pores spaced at 200 μm in a stirred-cell (batch, LDC-1) and crossflow (continuous, AXF-1) system for TEL formation. By controlling the feed flow rate of the API and solvent, through the membrane pores as well as the antisolvent flow, it was possible to tightly control the micromixing and with that to control the crystal nucleation and growth. Batch crystallization without the membrane resulted in an inhomogeneous crystallization process, giving a mixture of crystalline and amorphous TEL materials. The rate of crystallization was controlled with a higher DMSO content (4:1 DMSO/DI water), resulting in slower crystallization of the TEL material. Both membrane setups, stirred batch and the crossflow, yielded the amorphous TEL particles when deionized water was used, while a crystalline material was produced when a mixture of DI water and DMSO was used.

A cellular NO sensor based on aggregation-induced electrochemiluminescence and photoelectron transfer of a novel ruthenium(II) complex

Here, we present a dual amplification strategy of electrochemiluminescence (ECL) based on aggregation-induced and photoelectron transfer (PET) inhibition using a designed ruthenium-based complex for the highly sensitive detection of nitric oxide (NO). A novel ruthenium(II) complex ([Ru(phen)2(DA-phen)]2+, DA-phen: 5,6-diamino-1,10-phenanthroline) was synthesized that uses the O-diaminophenyl group for specific recognition of NO and the ruthenium metal center with 1,10-phenanthroline as the luminophore. In the first step, the 1,10-phenanthroline groups function as the aggregation part. Increasing the volume fraction of a poor solution (H2O: fw, v%) in the DMSO mixture system from 0% to 80% yielded an increase in the fluorescence (FL) and electrochemiluminescence (ECL) intensities by 3- and 42-fold when compared with the FL and ECL intensities in pure DMSO, respectively. The second step involves a PET process. Reacting the complex with NO in physiological pH aqueous media under aerobic conditions to afford its triazole derivative, [Ru(phen)2(TA-phen)]2+ (TA-phen: 5,6-triazole-1,10-phenanthroline), inhibited the electron transfer process, yielding a remarkable further increase in the FL and ECL efficiencies of the Ru(II) complex. The ECL intensities was 86-fold higher in the presence of NO. This dual amplification strategy enabled the sensitive detection of NO from 1.8 × 10–10 to 1.8 × 10–5 M with a detection limit of 60 pM (S/N = 3) and offered excellent specificity with no detectable interference by RNS and metal ions. Furthermore, selective NO detection in cells was achieved using this complex. Thus, this assay should be suitable for applications in environmental toxicology research and early clinical diagnosis.

Rotational dynamics study of structurally similar (medium sized) coumarin dyes in aqueous mixtures of DMSO and DMA

The rotational diffusion dynamics of four medium sized, structurally similar, polar Coumarin dyes namely, Coumarin-478 (C478), Coumarin-480 (C480), Coumarin-519 (C519), and Coumarin-523 (C523) has been studied at room temperature in aqueous DMSO and aqueous DMA by using steady state and time resolved fluorescence depolarization techniques. All the probes exhibited faster rotation in organic solvent rich zone than in water rich zone that resulted in a downward bent “hook profile” of rotational reorientation time as a function of viscosity. A faster rotational diffusion is observed for C523 in contrast to the other three solutes in both the aqueous solvent mixtures. The difference between τr values at iso-viscous points is smaller in case of aqueous DMA than in aqueous DMSO which reveals the importance of dielectric friction. Since both solutes and solvents are polar in nature, the Nee-Zwanzig (NZ) and van der Zwan and Hynes (ZH) dielectric friction theories have been used along with Stokes-Einstein-Debye (SED) hydrodynamic theory to assess the experimental results and understand the microfriction experienced by the solute. An important aspect of this work is to establish a relation between viscosity and hydrogen bond strengths at varying compositions of solvent mixtures as well as hydrogen bond strength between solute and solvents with the help of Gaussian 09 software. The H-bond strength thus calculated is found to be higher at a composition where the viscosity is the maximum. It provides an additional support to the experimental results.