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Chemistry of Carbonate-Sulfur Flux
Q. Won Choi,Choi Han,Chang So-Young,Pyun Chong-Hong,Kim Chang-Hong Korean Chemical Society 1994 Bulletin of the Korean Chemical Society Vol.15 No.12
Reactions of alkaline metal carbonates with sulfur are investigated in detail. The evolution of CO and a trace of $SO_2$ were observed in the course of reaction with major component of polysulfides. Some evidences that the reaction proceeds with breaking of terminal sulfur-sulfur bond in the sulfur polymer, and forming CO, $SO_2$ and polysulfide are presented. Polysulfides have the role of keeping free sulfur and allow it to react with other chemicals to rather high temperatures.plexes, whereas the binuclear and mononuclear complexes of Mn$^{2+}$ and Co$^{2+}$</TE. showed similar reactivities. The nature of the ligands bound to copper did not influence the reactivity of the binuclear copper complexes so long as copper ions were held in close proximity. A metal-iodosylbenzene complex, such as suggested previously for Lewis acidic metal complex-catalyzed epoxidat.n by iodosylbenzene, is proposed as the active epoxidizing species. Some mechanistic aspects are discussed as well.
Kinetics and Mechanism of $N_2H_4-KBrO_3$ Reaction in the Presence of Allyl Alcohol$^\dag$
Choi, Q.-Won,Chung, Keun-Ho Korean Chemical Society 1986 Bulletin of the Korean Chemical Society Vol.7 No.6
Kinetics and Mechanism of $N_2H_4-KBrO_3$ reaction in the presence of allyl alcohol have been studied. The pseudo-first order rate constant for gas evolution was found to be $10^{-4}{\sim}10^{-2}\;sec^{-1}\;at\;25.0{\pm}0.1^{\circ}C$, increasing with concentration of hydrogen ion. When concentrations of sulfuric acid and allyl alcohol are both sufficiently high, the following overall reaction explains experimental results reasonably well: $N_2H_4\;+\;BrO_3^-\;+\;H^+\;{\to}\;N_2\;+\;HOBr\;+\;2H_2O,\;CH_2\;=\;CHCH_2OH\;+\;HOBr\;{\to}\;CH_2-OHCHBrCH_2OH$. More complicated reaction mechanisms at lower acidity conditions have been contemplated.
Differential Titrimetric Determination of Bismuth$^1$
Choi, Q.-Won,Lim, H. S. Korean Chemical Society 1983 Bulletin of the Korean Chemical Society Vol.4 No.5
A precise EDTA titrimetric method involving a weight titration of major portion with solid reagent followed by titration of the remainder with a very dilute standard solution has been developed for the determination of bismuth. When the end point is determined by means of amperometry with a rotating mercury electrode, the error in bismuth analysis is less than 0.01 % even when $Pb^{2+}$, $Zn^{2+}$, or $Cd^{2+}$ is present. However, copper interferes appreciably and masking with thiourea gives too low results.
Stoichiometry of Hydrazine-Bromate Reaction in Acid Media
Choi, Q.Won,Jung, Jin Korean Chemical Society 1971 대한화학회지 Vol.15 No.4
Stoichiometry of hydrazine-bromate reaction has been studied in acid media of varying compositions, elucidating the effects of bromide and chloride ions in sulfuric acid, perchloric acid, hydrochloric acid, and hydrobromic acid at varying concentrations of hydrogen ion and cupric ion. The study shows that the number of red-ox equivalent consumed by one mole of hydrazine becomes practically 4.00 if the concentrations of bromide and hydrogen ions are kept higher than 0.1M and 6M, respectively. The presence of copper tends to reduce the bromate consumption by hydrazine in an irregular manner, but such an effect becomes unimportant if the concentrations of bromide and hydrogen ions are kept sufficiently high.
Determination of Rate Constants in Competitive Consecutive (Series) Second-Order Reaction
Q. Won Choi Korean Chemical Society 1984 Bulletin of the Korean Chemical Society Vol.5 No.3
The kinetics of the reactions of the type A + B \longrightarrow^{k_1} C + E and B + C \longrightarrow^{k_2} D + F has been analyzed and a method of obtaining approximate values of $k_1\;and\;k_2$ for the cases where $k_2$ ${\gg}$ $k_1$ is proposed.
Purification of TiCl$_4$ by Adsorption Technique
Choi Q. Won,Lee Kyung Ae Korean Chemical Society 1988 Bulletin of the Korean Chemical Society Vol.9 No.1
Titanium tetrachloride is purified using adsorption column packed with activated silica gel. When 120 ml of titanium tetrachloride was passed through an adsorption column filled with 7 g silica gel, iron content in titanium tetrachloride has been reduced from 7 ppm to less than 1 ppm, and aluminum from 46 ppm to 11 ppm, while silicon content being unchanged at about 60 ppm.
박원희,이기준,최규원 한국화학공학회 1964 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.2 No.2
The roasting of molybdenum sulfide cake, a by-product at the chemical processing plant of tungsten ore in Sangdong, Korea, and its optimum operational conditions have been studied. Molybdenum sufide cake was pelletized cylindrically to be packed in the bed, and roasted with the air heated by propane directly. The roasting reaction itself was observed to be extremely rapid and exothermic. The effects of the air rate and inlet air temperature were investigated and the optimum operational conditions were determined. The packed bed height and pellet size also affect the reaction rate remarkably. As the parameter of overall reaction rate, the overall heat liberated rate was calculated from the experimental data and compared with overall weight decrease rate obtained graphically from the thermal balance roasting data. It was found that the molybdenum sulfide cake can be processed economically by the proposed roasting method at the evaluated optimum air rate and inlet air temperature to produce the product containing more than 90% MoO₃ and less than 2% S, which is considered to be rather adequate for the next process of purifying by the method of sublimation.
Oxidation-Reduction Titration Curve Both Half Reactions Homogeneous in Coefficient
최규원,Choi, Q-Won Korean Chemical Society 1967 대한화학회지 Vol.11 No.4
균일계수 산화환원 적정에 있어서의 전위의 적정분율에 따른 변화을 나타내는 정확한 방정식을 얻었다. 이 방정식은 정정곡선이 시약의 농도에 무관계함을 알려준다. 또한 전위차적정범위 종말점의 예민도는 반전지의 기준전위의 차는 몰론, 각 반반응에 관여하는 전자수에 따라 심한 영향을 받음을 알려준다. 적정곡선의 변곡점이 당량점과 일치하지 않음을 증명하였다. 또한 적정단계에 따른 반응의 완결도를 평형상수식을 토대로 하여 해석하였다. 이 결과는 산화환원 이외의 평형에도 적용된다. An exact expression of the titration fraction as a function of the potential is derived for the cases where the coefficients of the both half reactions involved in the titration are homogeneous. It shows that the potential is independent of the concentration of the reagents not only at the equivalence point but also at all titration fractions. The sharpness of the end point detection by potentiometric method is shown to depend not only on the difference of the normal potentials involved but also strongly on the number of electrons transferred in each half reaction. The inflexion point of the potentiometric titration curve is shown to be slightly off from the equivalence point, including the cases where the number of electrons involved are equal. Completeness of the reaction in the course of titration is analyzed, too, mostly in terms of equilibrium constant, thus most of the results are applicable to any type of equilibrium in a single phase with particular relationship of coefficients of chemical equation.