• Journal of the Korean Chemical Society
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• v.21 no.4
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• pp.227-234
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• 1977

The reaction of phenylhydrazine with bromine in sulfuric acid solution has been studied kinetically. The pseudo-second-order rate constant is approximately inversely proportional to hydrogen-ion concentration when the concentration of sulfuric acid is lower than 1M. arom the study of the effect of potassium bromide concentration on the rate constant, it is concluded that both neutral bromine and tribromide ion participate in the reaction, the rate constants in 0.01M $H_2SO_4$ being $5{\times}10^5M^{-1},sec^{-1}\;and\;0. 7{\times}10^5M^{-1},sec^{-1}$, respectively at $20^{\circ}C$. The pseudo-second-order rate constant of 2.4-dinitrophenylhydrazine-bromine reaction is independent of hydrogen ion concentration. From the KBr addition experiment, the rate constants for $Br_2\;and\;Br_3^-$ were obtained as $1.2{\times}10^5M^{-1},sec^{-1}\;and\;2.0{\times}10^4M^{-1},sec^{-1}$, respectively.

• YAKHAK HOEJI
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• v.37 no.4
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• pp.370-382
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• 1993

In order for formulation of rectal containing OMZ, the OMZ suppositories were prepared using water-soluble base, PEG 4000 base and oil-soluble base, Witepsol H 15. Chemical stability of OMZ in suppositories was increased when Witepsol H 15 was used as a suppository base and arginine was added as a stabilizer. The decomposition of OMZ in suppository bases followed the first-order kinetics and their rate constants were 0.11 day $^{1}(t_{1/2}$=/6.25 days) for Witepsol H 15 suppository and 0.48 day $^{1}(t_{1/2}$=/1.43 days) for PEG 4000 suppository, respectively. On the other hand, the decomposition rate constants of Witepsol suppository and PEG suppository stabilized with arginine were 3.89$\times$10$^{-3}$(t$_{1/2}$=171.1 days) and 8.76$\times$10$^{-3}$ day $^{1}(t_{1/2}=79.9 days), respectively. Shelf-lives of the Witepsol and PEG suppositories stabilized with arginine were t$_{90%}$=291.8 days and t$_{90%}$=282.1 days at $35^{\circ}C$ and 75% RH, respectively. The dissolution test of OMZ suppositories was performed by rotating dialysis cell(RDC) method and the release rate constant was calculated by the simplified Higuchi's equation, Q'=K' t$^{1/2}$. Dissolution of OMZ from suppositories was augmented as arginine was added, particle size of OMZ was reduced and a suitable surfactant such as SLS was added. RDC method was more appropriate and available than Paddle method to evaluate the dissolution rate of lipophilic-base suppositoies. Arginine was found to be a very useful exipient for the enhancement of stability and dissolution of OMZ in suppositories.

• Korean Journal of Food Science and Technology
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• v.23 no.3
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• pp.355-359
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• 1991

Effects of temperature and pH on thermal degradation of monosodium glutamate(MSG) were investigated during heating of 2% MSG solution at $100{\sim}200^{\circ}C\;and\;pH\;4{\sim}9$. The results showed that the degradation of MSG was very significantly affected by heating temperature and pH. Three hours of heating at $pH\;4\;and\;120^{\circ}C$ resulted appr. 73% MSG degradation while 3 hours at $100^{\circ}C$ decreased only 12%. The comparison study of initial rate of MSG degradation and degradation rate constants showed the highest degradation rate and rate constant and low values in the range of $pH\;6{\sim}8{\sim}$. The values of activation energy calculated from linear relationship of rate constants and 1/T were 18.3 and 9.2 kcal/mole for pH 4 and 5, respectively.

• Bulletin of the Korean Chemical Society
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• v.11 no.5
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• pp.391-395
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• 1990

The kinetics of thermnal cis-trans isomerization reaction of 1-bromopropene(1-BP) was studied at temperatures from 620.8 to 753.15 K over the pressure range 0.17-50.3 Torr. Both the inhibition effect by cyclohexene or propene and the catalytic effect by HBr showed a radical process as the main mechanism of the isomerization. In the suppression of the radical process by the inhibitors, the molecular process also contributed to overall reaction rate. The reactions demonstrated the first order kinetics under both uninhibited and inhibited conditions and could be represented by the expressions (R = 1.987 cal/mol/K) $k_{un}/s^{-1} = (3.45{\pm}1.50){\times}10^{11}$exp$[(- 48100{\pm}2000)/RT]\;k_{ink}/s^{-1} = (2.98{\pm}1.40){\times}10^{12}$exp$[(- 55800{\pm}1800)/RT]$> where $k_{un}$ is the observed rate constant of cis-1-bromopropene(1-B$P_c$) to trans-1-bromopropene(1-B$P_t$) under uninhibited condition at initial pressure of 50 Torr and $k_{ink}$ is the rate constant under maximal inhibition by cyclohexene. The ratio of rate constants for bromine atom elimination from the allylic hydrogen of reactant(1-BP) and from the inhibitors, propene and cyclohexene, were measured from the observed rates of the uninhibited and inhibited reactions. The inhibition efficiencies of cyclohexene and propene were compared kinetically from the rate constants and shown to give good agreement with the previous results reported from other alkyl bromide pyrolyses.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.36.3-37
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• 2009

This is an attempt to improve a formula to predict variations of geomagnetic storm indices (Dst) from solar wind parameters. A formula which is most widely accepted was given by Burton et al. (1975) over 30 years ago. Their formula is: dDst*/dt = Q(t) - Dst*(t)/$\tau$, where Q(t) is the Dst injection rate given by the convolution of dawn-to-dusk electric field generated by southward solar wind magnetic field and some response function. However, they did not clearly specify the response function. As a result, misunderstanding seems to be prevailing that the injection rate is proportional to the dawn-to-dusk electric field. In this study we tried to determine the response function by examining 12 intense geomagnetic storms with minimum Dst < -200 nT for which solar wind data are available. The method is as follows. First we assume the form of response function that is specified by several time constants, so that we can calculate the injection rate Q1(t) from the solar wind data. On the other hand, Burton et al. expression provide the observed injection rate Q2(t) = dDst*/dt + Dst*(t)/$\tau$. Thus, it is possible to determine the time constants of response function by a least-squares method to minimize the difference between Q1(t) and Q2(t). We have found this simple method successful enough to reproduce the observed Dst variations from the corresponding solar wind data. The present result provides a scheme to predict the development of Dst 30 minutes to 1 hour in advance by using the real time solar wind data from the ACE spacecraft.

• Journal of the Korean Ceramic Society
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• v.15 no.1
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• pp.21-27
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• 1978

Hadong Kaolin (Halloysite) was granulated cylindrically and treated with 1N aqueous sodium hydroxide solution for 6-48 hrs at 60-10$0^{\circ}C$. The crystalling structure of surface of the products was studied by X-ray powder diffraction method. The reaction rate of halloysite to sodium A zeolite showed a gradual decrease from surface to inner layer. At the surface layer, the reaction mechanism was observed as first order consecutive reaction as follows: halloysitelongrightarrowamorphous aluminosilicatelongrightarrowsodium A zeolitelongrightarrowhydroxysodalite By applying the above reaction mechanism, the rate constants and activation energies was measured.

• Bulletin of the Korean Chemical Society
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• v.28 no.8
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• pp.1410-1412
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• 2007

• Journal of the Korean Chemical Society
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• v.13 no.4
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• pp.249-261
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• 1969

Studies of photochemical reactions of the pure oxygen atmosphere are made using reaction rate constants and atmospheric data available in the latest literature. The daytime and nighttime variations in atomic oxygen and ozone are computed, based on three different conditions: 1) photochemical equilibrium, 2) direct integrations of the rate equations with modifications and approximation to the equations, and 3) by numerical integrations. The departure from the photochemical equilibrium concentrations during day and nighttime are discussed by comparing the results obtaind from the three conditions.

• Journal of Pharmaceutical Investigation
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• v.25 no.4
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• pp.283-289
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• 1995

The aim of this study is to increase the solubility and dissolution rate of clonixin by inclusion complex formation. Inclusion complexes of clonixin, a non-steroidal antiinflammatory drug, with ${\beta]-cyclodextrin$ were $2-hydrolrypropyl-{\beta]-cyclodextrin$ were prepared by freeze drying method. Inclusion complex formation of clonixin with cyclodextrins was determined by UV, IR and DSC. The apparent stability constants were calculated from the phase solubility diagrams. Dissolution rate and solubility of clonixin in water markedly increased by the complex formation.

• Bulletin of the Korean Chemical Society
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• v.9 no.1
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• pp.17-21
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• 1988

A mechanistic study on the chemiluminescence resulting from the reaction between bis(2,4,6-trichlorophenyl)oxalate(TCPO) and hydrogen peroxide in the presence of fluorescent polycyclic aromatic hydrocarbons in a viscous phthalate medium has been conducted. The rate determining step, decay rate constants, and relative quantum efficiencies yielded by varying the concentration of reagents generally support an existing mechanism. However, a reaction between TCPO and sodium salicylate was not observed.