• Bulletin of the Korean Chemical Society
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• v.21 no.7
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• pp.685-689
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• 2000

The complexation reaction between Pb2+,TI and Cd2+ions and macrocyclic ligands, 18-crown-6 ( 18C6) and dibenzo- 18-crown-6 (DB 18C6), was studied in dimethylsulfoxide (DMSO)-nitromethane (NM) and dimethyl-formamide (DMF)-nitromethane binary system s by square wave polarography (SWP) technique. The stoichiometry and stability of the complexes were determined by monitoring the shifts in half-waves or peak potentials of the polarographic waves of metal ions against the Iigand concentration. In most cases, the stability constants of complexes increase with increasing amounts of the nitromethane in mixed binary solvents used in this study. The complexes formed between 18C6 and DB18C6 and these metal cations in all cases had a stoichiometry of 1 : 1. The results obtained show that there is an inverse relationship between the formation constant of complexes and the donor number of solvents based on a Gatmann donocity scale and the stability constants show a high sensitivity to the composition of the mixed solvent systems. A linear behavior was observed for variation of log Kf of I8C6 complexes vs the composition of the mixed solvent systems in NM/DMSO and NM/DMF,but a non-linear behavior was observed in the case of DB 18C6 complexes in these binary systems. In most of the systems investigated, the Pb2+ cation forms a more stable complex with the 18C6 than other two cations and the order of selectivity of this Iigand for cations is: Pb2+ > TI+,Cd2+.

• Journal of the Korean Chemical Society
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• v.46 no.6
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• pp.528-534
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• 2002

We have studied to find the optimum electrolyte that satisfied high ionic conductivity, large elec-trochemical window, etc in Li-ion battery. And also studied were the effect of a passive film on carbon anode surface,which is formed by solvent decomposition during the initial charge process. Electrochemical properties of the passive film formed on carbon anode surface investigated and explained as the volumetric ratio of the mixed solvents. The results of scanning electron microscopy, chronopotentiometry, cyclic voltammetry, impedance spectroscopy revealed that the electrochemical properties of the passive film were varied with the ionic conductivity of the electrolyte including the mixed solvents.

• Applied Chemistry for Engineering
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• v.32 no.5
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• pp.532-540
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• 2021

Sodium dodecanoyl-4-oxybenzenesulfonate (DOBS) salt is a substance that exhibits effective bleaching and antimicrobial abilities at low temperatures. A mild and efficient synthesis method of DOBS starting from dodecanoyl chloride and sodium 4-hydroxybenzene sulfonate was investigated under alkaline conditions using a water (W)-polar aprotic solvent system. First, the reaction was carried out using only water as a solvent system with the variables of temperature and time. The yield was found to be as low as about 5% in most cases under the reaction conditions of more than 30 ℃ and 1 h. In order to develop an efficient solvent system, the effect on the yield of DOBS was evaluated in various solvent systems which were prepared by changing the type of polar aprotic solvents while mixing them with the water. A solvent system in which acetone (AC) and water were mixed showed the best yield and about 82 % under mild reaction conditions (30 ℃, 1 h and atmospheric pressure) was obtained. The prepared DOBS showed good bleaching and antimicrobial activities indicating that it could be used an excellent bleach activator.

• Applied Chemistry for Engineering
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• v.18 no.3
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• pp.234-238
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• 2007

Highly conducting Polypyrroles soluble in organic solvents were synthesized using functional doping agents, such as mixed dopants [sodium di(2-ethylhexyl)sulfosuccinate (DEHSNa) Naphthalenesulfonic acid (NSA), DEHSNa Toluenesulfonic acid (TSA), DEHSNa Dodecylbenzensulfonic acid (DBSA)] and mixed oxidants [$(NH_4)_2S_2O_8{\cdot}FeCl_3$, $(NH_4)_2S_2O_8{\cdot}Fe_2(SO_4)_3$]. Ppy-DEHS powder using an oxidant, such as $(NH_4)_2S_2O_8$ (10 wt%/vol.) showed higher solubility than the mixed dopant (DEHSNa NSA, 3 wt%/vol.) and mixed oxidant [$(NH_4)_2S_2O_8{\cdot}Fe_2(SO_4)_3$, 4 wt%/vol.] in DMF solvent. But Ppy-DEHS free standing film using a mixed dopant, such as DEHSNa NSA (16 S/cm) and a mixed oxidant, such as $(NH_4)_2S_2O_8{\cdot}Fe_2(SO_4)_3$ (13 S/cm) cast from DMF solvent showed higher electrical conductivity than $(NH_4)_2S_2O_8$ (2 S/cm). For the Ppy-DEHS films using various condition cast from DMF solvent, three dimensional various range hopping model (3D VRH ; $\{{\sigma}_{dc}(T)={\sigma}_oexp[-(T_o/T)^{1/4}]\}$) provided fit to the results of temperature dependence of electrical conductivity measurement.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.5 no.1
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• pp.48-58
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• 1995

This study was performed to find out the exposure level of mixed organic solvents, excretion of urinary hippuricacid and subjective symptoms according to the exposure of organic solvents of female workers who works on 5 shoes manufacturing industries in Taejon City from 24, september to 20, october 1993. The studied groups were divided into 3 groups that were consist of direct exposure group(48 workers), indirect exposure group(49 workers) and non-exposure group(68 workers) to the organic solvents. The exposure levels of toluene of direct exposure group which $89.86{\pm}56.20ppm$ had higher than that of indirect exposure group which had $40.23{\pm}47.21ppm$. In the exposure level of mixed organic solvent(R-value), direct exposure group was $2.84{\pm}1.53$ and exceeded approximatly 3 times the R-value. Whereas, indirect exposure group was not exceeded the R-value as $0.80{\pm}0.61$. In the excretion level of urinary hippuric acid, direct exposure group was $1.78{\pm}1.25g/l$, indirect exposure group was $1.22{\pm}0.93g/l$ and non-exposure group was $0.51{\pm}0.18g/l$ respectively. Therefore both direct exposure group and indirect exposure group were significantly higher than non-exposure group(P<0.01). In the correlation between toluene levels and urinary hippuric acid level, the direct exposure group had positive correlation(R=0.8309, P<0.01), also indirect exposure group had positive correlation(R=0.5859, P<0.05) and also in the correlation between the R value of mixed organic solvents and the urinary hippuric acid levels, the direct exposure group had positive correlation(R=0.4492, P<0.05), and indirect exposure group had ositive correlation(R=0.7911, P<0.01). In the complain rates of the worker's subjective symptoms at work, both direct exposure group and indirect exposure group were higher than non-exposure group(P<0.05, P<0.01). But the sujective symptoms of "floating sensation" of direct exposure group had significantly higher than indirect exposure group. In the percent of subjective symptoms complaints during the worker's daily life, both direct exposure group and indirect exposure group had generally more statistical significance than nonexposure group(P<0.01), direct exposure group had not statistical significant difference from indirect exposure group. As the results mentioned above, it has been analysed that the indirect at the adjacent manufaturing process are exposed to the considerable amount of solvent. Therefore, I think that there should be the betterment of surrounding through the complete working environment management to the occurrence source of the organic solvent, the changes of health management system to the indirect-exposed workers, and the systematic management of the special medical examination and the like.

• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.1945-1950
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• 2010

Solvent extraction experiments of Pt(IV), Pd(II) and Rh(III) by Alamine336 were performed from the mixed chloride solutions. In the HCl concentration range from 1 to 5 M, most of Pt and Pd were extracted from the mixed solutions. However, the extraction percentage of Rh was much smaller than that of Pt and Pd. Lower concentration of Alamine336 in strong HCl solution led to higher separation factor of Rh from Pt and Pd. Adding $SnCl_2$ to the mixed solutions increased the extraction percentage of Rh, while the extraction percentage of Pt and Pd was little affected. Our results showed that selective separation of Rh or coextraction of the three platinum group metals from the mixed solution would be possible by adjusting the extraction conditions.

• Bulletin of the Korean Chemical Society
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• v.23 no.1
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• pp.65-70
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• 2002

We have evaluated the specific hydroxyl group-solvent and carbonyl group-solvent interactions by using an Alltima C18 stationary phase and by measuring the retention data of carefully selected solutes in 60/40, 70/30, and 80/20(v/v%) acetonitrile/water eluents at 25, 30, 35, 40, 45, and 50 oC. The selected solutes are phenol, acetophenone, alkylbenznes(benzene to hexylbenznene), 4 positional isomers of phenylbutanol, 5-phenyl-1-pentanol, 3 positional isomers of alkylarylketone derived from butylbenzene, and 1-phenyl-2-hexanone. The magnitudes of hydroxyl group-acetonitrile/water specific interaction enthalpies are larger than those of carbonyl group-acetonitrile/water specific interaction enthalpies in general while the magnitudes of carbonyl group-methanol/water specific interaction enthalpies are larger than those of hydroxyl group-methanol/water specific interactions. We observed clear discrepancies in functional group-solvent specific interaction among positional isomers. The variation trends of solute transfer enthalpies and entropies with mobile phase composition in the acetonitrile/water system are much different from those in the methanol/water system. The well-known pocket formation of acetonitrile in aqueous acetonitrile mixtures has proven to be useful to explain such phenomena.

• Korean Journal of Materials Research
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• v.26 no.3
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• pp.109-116
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• 2016

To achieve the fabrication of high-quality Ag-coated Cu particles through a wet chemical process, we reported herein pretreatment conditions using an ammonium-based mixed solvent for the removal of a $Cu_2O$ layer on Cu particles that were oxidized in air for 1 hr at $200^{\circ}C$ or for 3 days at room temperature. Furthermore, we discussed the results of post-Ag plating with respect to removal level of the oxide layer. X-ray diffraction results revealed that the removal rate of the oxide layer is directly proportional to the concentration of the pretreatment solvent. With the results of Auger electron spectroscopy using oxidized Cu plates, the concentrations required to completely remove 50-nm-thick and 2-nm-thick oxides within 5 min were determined to be X2.5 and X0.13. However, the optimal concentrations in an actual Ag plating process using Cu powder increased to X0.4 and X0.5, respectively, because the oxidation in powder may be accelerated and the complete removal of oxide should be tuned to the thickest oxide layer among all the particles. Back-scattered electron images showed the formation of pure fine Ag particles instead of a uniform and smooth Ag coating in the Ag plating performed after incomplete removal of the oxide layer, indicating that the remaining oxide layer obstructs heterogeneous nucleation and plating by reduced Ag atoms.

• Analytical Science and Technology
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• v.21 no.2
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• pp.117-122
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• 2008

Dual scintillator for simultaneous alpha- and beta-ray counting used by detection materials of a surface contamination monitor was developed. In this study, preparation method was not a heat melting method but a solvent method, by which the counting material was manufactured by dissolving the polymer materials with solvent. It was simplified the preparation process. Plastic scintillator for beta-ray counting was prepared by solidifying the casting solution mixed with organic scintillator, polymer, and solvent. ZnS(Ag) scintillator layer was prepared by screen printing the paste solution mixed with ZnS(Ag), paste, and solvent onto the plastic layer. The good counting ability for alpha- and beta-ray using the ZnS(Ag)/plastic dual scintillator prepared and possibility for the counting material of surface contamination monitor was confirmed.

• Elastomers and Composites
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• v.29 no.3
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• pp.226-233
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• 1994

The properties of the mixed prepolymer-urethane in the range of 10-40 phr were observed. LBR and LCR have same functional group but different in structure of molecular. The viscosity of mixture depending on content of rubber, adhesive strength, thermal property and compatibility with a diluted solvent are as follows: 1. The viscosity of the mixture was influenced by solubility of the diluent for urethane resin and liquid rubber. 2. Adhesive strength showed the highest value at 30phr rubber, decreased gradually at above 30phr rubber. And LBR revealed better physical property than that of LCR. 3. The most effective factors affecting adhesive strength are molecular structure of rubber, the type of solvent, and volatility. 4. Urethane resin containing LBR showed better compatibility for solvent and faster drying velocity. 5. LBR showed more favorable compatibility and dispersion state than those of LCR by analyzing the results of SEM.