Stability of lyophobic sols

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.

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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.

     

Photopolymerization of methyl methacrylate with the use of bromine as photoinitiator

Low concentrations of bromine (0.008–0.06M) were used to initiate photopolymerization of MMA in bulk and in diluted (near bulk) systems, the diluents or solvents used being benzene, toluene, dioxane, tetrahydrofuran, carbon tetrachloride, chloroform, methylene chloride, and methanol. Polymerization in bulk follows usual free-radical kinetics. Inert solvents (benzene, toluene) as well as the other solvents used enhance the rate of polymerization MMA even when used in the range of catalytic concentrations (0.04–0.4M). An initiation mechanism involving solvent molecules appears to be predominant in diluted systems.     

Photograft Copolymerization of Methyl Methacrylate on Wool Using Ce4+ -Oxalic Acid Redox Initiator in a Limited Aqueous System

Abstract

Photograft copolymerization of methyl methacrylate on reduced wool (reduction done by treatment with thioglycollic acid, TGA) was studied at nearly 30°C using a Ce⁴⁺ -oxalic acid redox initiator system in a limited aqueous system (2.7 mL water for 0.15 g wool). Reduction of wool for 16 h with 15% TGA solution produced optimum grafting effects. Percent grafting and grafting efficiency under different sets of conditions were studied and compared, and the mechanism of grafting discussed. Generation of grafting sites (radical centers) on reduced wool was more effective in the presence of light than in the dark. Percent grafting of 250–350% and grafting efficiency of 65-80% over a conversion range of 60–90% in 3–5 h were easily obtained.     

A quantum chemical survey of metalloporphyrin-nitrosyl linkage isomers: insights into the observation of multiple FeNO conformations in a recent crystallographic determination of nitrophorin 4

Using density functional theory-based geometry optimizations, we have searched for eta(1)-NO, eta(1)-ON (isonitrosyl), and eta(2)-NO (side-on bound NO) linkage isomers of a number of metalloporphyrin-NO complexes, M(Por)(NO)(L), where Por = porphinato dianion, M = Mn(II), Fe(II), Fe(III), Ru(II), Ru(III), Co(II), and Rh(II), and L = no ligand, SMe, Ph, and imidazole. The eta(1)-NO isomer had the lowest energy in all cases, and the isonitrosyl isomer was also located as a higher energy potential energy minimum in a number of cases. The eta(2)-NO isomer was only located as a minimum for Mn(II) (L = no ligand), Fe(III) (L = no ligand), and Ru(III) (L = Ph, imidazole, pyrdine), suggesting that an [MNO](6) electron count is important for stabilization of the eta(2) mode of ligation. However, in the presence of axial ligands L, the side-on isomers of [FeNO](6) complexes were not stable and opened up to an unusual geometry where the FeN(O) and NO vectors were tilted in opposite directions relative to the heme normal. Exactly such a geometry, as well as a "normal" upright geometry, has been observed in a recent crystallographic determination of nitrophorin 4 (Nature Struct. Biol. 2000, 7, 551), a salivary protein from the blood-sucking insect Rhodnius prolixus. Together, the calculated and experimental result illustrate the extreme softness of the FeNO potential energy surface toward various forms of tilting and bending deformations.     

Solvent‐Mediated Functionalization of Benzofuroxan on Electron‐Rich Ruthenium Complex Platform

An unprecedented reactivity profile of biochemically relevant R‐benzofuroxan (R=H, Me, Cl), with high structural diversity and molecular complexity on a selective {Ru(acac)₂} (acac=acetylacetonate) platform, in conjugation with EtOH solvent mediation, is revealed. This led to the development of monomeric [Ru^III(acac)₂(L^1R)] ( 1 a – 1 c ; L^1R=2‐nitrosoanilido derivatives) and dimeric [{Ru^II(acac)₂}₂(L^2R)] ( 2 a – 2 b ; L^2R=(1E,2E)‐N¹,N²‐bis(2‐nitrosophenyl)ethane‐1,2‐diimine derivatives) complexes in one pot with a change in the metal redox conditions. The functionalization of benzofuroxan in 1 and 2 implied in situ reduction of N=O to NH^? in the former and solvent‐assisted multiple N?C coupling in the latter. The aforesaid transformation processes were authenticated through structural elucidation of representative complexes, and evaluated by their spectroscopic/electrochemical features, along with C₂D₅OD labeling and monitoring of the impact of substituents (R) in the benzofuroxan framework on the product distribution process. The noninnocent potential of newly developed L¹ and L² in 1 and 2 , respectively, was also probed by spectroelectrochemistry in combination with DFT calculations.     

Estimation of underground water radon danger in Bakreswar and Tantloi Geothermal Region,India

The main aim of the study is to present an evaluation of radon concentration in underground water of Bakreswar and Tantloi geothermal region which is mainly used for drinking purposes of the local people. Water samples were collected from tube-wells at 173 different locations. The radon (²²²Rn) concentration level was observed to fluctuate widely between 3.3 and 803.8 Bq/l with an average of 106.8 Bq/l. Nearly 42% of the samples had radon concentration above the safe limit of 100 Bq/l recommended by World Health Organisation (WHO) and European Union Commission (EU). Considering the WHO and International Commission on Radiological Protection recommended water consumption rate for adults (730 l/year) the corresponding total annual effective dose of the samples were estimated to assess the probable health risk. Total annual effective dose of the samples were varied between 16.72 and 4079.47 µSv/year with an average value of 541.92 µSv/year. About 95% samples exceed the WHO and EU Commission proposed safe limit of 100 µSv/year.     

Effect of N-doping on hard carbon nano-balls as anode for Li-ion battery: improved hydrothermal synthesis and volume expansion study

Using an improved single-step hydrothermal method, mesoporous hard carbon nano-balls, with nitrogen doping, have been successfully synthesized. These materials exhibit good reversible charge capacity during half-cell tests. Gravimetric capacity for undoped nano-sized and micron-sized mesoporous hard carbon balls is 506 and 475 mAh g^?1, respectively. After nitrogen doping, the specific gravimetric capacities of both nano- and micron-sized carbon balls increase by 6.9 and 8%, respectively. Nitrogen doping enhances retention in specific capacity of both anode materials, particularly in nano-sized carbon balls with capacity retention of 83.9% after 100 cycles. The enhancement is attributed to a significant decrease in volume expansion due to the nitrogen doping. Density functional theory-based computation confirms the reduction of volume expansion by 60%. Improved electrochemical performance of nitrogen-doped hard carbon is due to the drop in volume expansion rate during lithiation along with increased porosity and electronic conductivity. Furthermore, this one-step synthesis can be extended to other carbon sources to get nitrogen-doped hard carbon with sizes varying from micro to nano.