• Journal of the Korean Chemical Society
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• v.10 no.3
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• pp.119-128
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• 1966

The glass electrode was empirically calibrated in methanol-and 2-propanol-water mixed solvents, by means of which the pH-meter reading could be converted to stoichiometric hydrogen ion concentration. The thermodynamic dissociation constants of hydrogen cupferrate in methanol-and 2-propanol-water solution were potentiometrically determined with the changes in composition of organic solvents at 0.01 and 0.05 of the ionic strength and 25$^{\circ}C$. The empirical formula of the constants with mole fraction (n) of the organic solvent are as follow: methanol-water solution $pK_a$= 2.24n + 4.29 at ${\mu}$ = 0.01 n = 0.0476∼0.642 $pK_a$ = 2.35n + 4.38 at ${\mu}$ = 0.05 n= 0.0446~0.642 2-propanol-water solution $pK_a$= 5.50n + 4.48 at ${\mu}$ = 0.05 n = 0.0253~0.259 The relationships between $pK_a$ of acetic acid, propionic acid and HCup and dielectric constant of some mixed solvents were discussed. It would be considered that the factors effecting $pK_a$ value of weak acid in mixed-solvent are not only dielectric constants but acid-base character and solvation effect of the solvent, etc.

• Journal of Environmental Health Sciences
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• v.24 no.2
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• pp.80-87
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• 1998

To evaluate the effects on health by exposure to low dose organic solvents, the author analyzed the air concentration of mixed organic solvents (toluene, xylene, butylacetate) at worker's breathing zone during painting, some laboratory findings of blood (WBC, RBC, Hb, Hct, SGOT, SGPT, TC, TG, HDL-C, LDL-C, IgG, IgM, IgA and IgE) and urine (hippuric acid, urinary protein, urobilinogen), surveyed the subjective symptoms those were obtained from 35 male workers exposed to mixed organic solvents, and 25 male workers not exposed to organic solvents who worked in car repair workshops in Taejon area from December 1, 1995, to February 29, 1996. The results were as follows: 1. The mean concentration of urinary hippuric acid of car painting worker group (organic solvent exposure group) was 0.76$\pm$ 0.21 g/l, which is significantly higher than that of non-exposed group. 2. In hematologic findings, the values of RBC, TC, LDL-C, IgG and IgE in the exposure group were significantly lower than those of the nonexposed group, but SGOT and SGPT in the exposure group were significantly higher than those of the non-exposed group. 3. Urinary hippuric acid levels showed positively correlated with toluene, urobilinogen and HDL-C levels, but those were negatively correlated with RBC, LDL-C, IgM levels. 4. Rates of the subjective symptoms such as "dizziness", "appetite loss", "weight loss", "palpitation", "chest tightness", "sore throat and eye discomfort", "tingling sense and acrodynia", "illusion or hallucination" and "decreaased motor power" were significantly higher in the exposure group than those of the non-exposed group.

• Bulletin of the Korean Chemical Society
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• v.26 no.7
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• pp.1037-1043
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• 2005

Kinetic study on the cleavage of N-methylphthalamic acid (NMPA) in mixed acidic aqueous-acetonitrile solvent reveals the formation of both phthalic anhydride (PAn) (through O-cyclization) and N-methylphthalimide (NMPT) (through N-cyclization). The formation of NMPT varies from $\sim$20% to $\sim$3% with the increase in the content of acetonitrile from 2 to 70% v/v. Pseudo first-order rate constants for the formation of PAn are more than 4-fold larger than those for the formation of NMPT at 2% v/v $CH_3CN$ in mixed aqueous solvents. Pseudo first-order rate constants for alkaline hydrolysis of NMPT reveal a nonlinear decrease with increase in the content of $CH_3CN$ in mixed aqueous solvents.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.350-353
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• 2004

This study was conducted for a rapid and simple method using GC/FID and SPME to dectermin gasonline and chlorinated solvents simultaneity. A sodium chloride concentration of 25%(vol/w) combined with such as magnetic stirried, an absorption time of 20min, an extraction temperature of 4$0^{\circ}C$, the volume of minimized 50mL of gaseous phase and a desorption time of 5min pleprovided the greatest sensitivity while maintaining analytical efficiency. Analytical parameter such as linearity was also evaluated. The linear range extend from 30 to 500ppb. The results of chlorinated solvents and gasoline mixed samples showed that solvents have been completely removed from the sample preparation step and more accurated than those obtained by the other methods.

• YAKHAK HOEJI
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• v.5 no.1
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• pp.20-23
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• 1960

The study of the isolative determination of the mixed weak bases of INAH and NA-Pas potentimetrically considering the properties of solvents for the INAH and Na-PAS, dielectric constant and solvative properties of solvents are described. The methanol: dioxan (4:1) and glacial acetic acid: dioxan (4:1) are studied first as the mixed solvent, using the N/10 perchloric acid and glacial acetic acid solution as the titrant. The authors found that there is no inflection on INAH with the methanol: dioxan solvent system and on Na-PAS at glacial acetic acid dioxan solvent system. By applying methanol glacial acetic acid dioxan (1:1:1) solvent system, Na-PAS and INAH were successfully determined isolatively from the mixed sample, showing the distinguished inflections respectively as shown in the titration curves in figures 3 and 4. It is found that this method could save considerable time for the isolative determination of the mixed sample of week bases as Na PAS and INHA which were quite difficult to be determined by the present routine at control laboratory.

• Journal of Preventive Medicine and Public Health
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• v.24 no.3 s.35
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• pp.314-327
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• 1991

To evaluate the effects on health by exposure to mixed organic solvents, the author analyzed some labortory findings of blood (hemoglobin, hematocrit RBC, WBC, SGOT, SGPT) and urine (protein, blood, sugar) that were obtained from 722 workers (male:446, female:276) who worked in plywood, painting and shoes factories in Pusan area from January to December, 1990. The result were as follows ; 1. The mean values of each hematologic findings were all within normal limit but there were significant differences at hematocrit, RBC, WBC, SGOT in male and at WBC, SGPT in female at the comparison of the mean values and the distribution according to the normal criteria by type of work. 2. There were no differences in urinalysis(protein, blood, sugar) by type of work. 3. In stepwise multiple regression, analysis of hematologic findings on age, working duration and type of work, regression coefficients on age and type of work were relatively high in male and female sub1, respectively. As a result of this study, it is considered that the measurement of WBC with morphology is significant in hematologic findings and instead of spot urine and urinstix, 24 hours urine and quantitative analysis is required in urinalysis in screening test for healthy status of workers who deal with the organic solvents.

• Korean Chemical Engineering Research
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• v.58 no.1
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• pp.92-97
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• 2020

In this study, the solubilities of a pharmaceutical compound, nifedipine, in three mixed solvents were determined. In addition, the nifedipine, that was dissolved in solvents (acetone, DMF, methylene chloride), was recrystallized using antisolvents (water, hexane, carbon dioxide) The external shape, size, and melting point of the crystallized nifedipine were measured. As the mixed solvents, acetone+water, DMF+water, and methylene chloride+hexane were used, and the solubility of nifedipine decreased with increasing antisolvent concentrations in the mixtures. In case of acetone+water, the solubility maximum was observed due to the density anomaly of the mixture, and this phenomenon was not observed in other systems. The crystallized nifedipine particles exhibited the bladed, equant, and prismatic habits, and the particles size was significantly reduced compared to the raw material. The average particle size of raw nifedipine was 337 ㎛, and the size of crystallized particles was in the range of 11.6~69.8 ㎛. All the crystallized nifedipine particles had the same thermal behavior and this result was not influenced by the change of solvent and antisolvent.

• Bulletin of the Korean Chemical Society
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• v.21 no.3
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• pp.351-352
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• 2000

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.1 no.1
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• pp.8-15
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• 1991

In order to visualize the distribution of workplace of which mixed solvent level in air exceeded the TLV of 1.0 (ACGIH), 17 thinners used in 44 painting workplaces were analysed with gas chromatography, and their levels in air were compaired with. 1. For detection rate of solvents in thinner was highest in case of toluene (76.4%), and decreased in orders of xylene (70.6%), methylisobutyl ketone (35.3%), acetone (35.3%), methyl ethyl ketone (23.5%), isopropylacohol (17.6%), n-hexane (17.6%), styrene (11.8%), and ethylacetate (11.8%). Average number of solvents detected was 3.0. 2. Detection rates of organic solvent by component category was highest in cases of aromatic hydrocarbons (52.9%), and decreased in orders of ketones (31.4%), alcohols (5.9%), n-hexane (5.9%) and esters (3.9%). The rate by regulatory category, the second category component was detected in 93.9% of total. 3. There was significant correlation (r=0.929, p<0.01)between detection rates of solvents in thinner and in air. 4. Among the total of 44 painting workplace, the rate of them of which level of mixed solvents in air was exceeded was highest in case of aromatic hydrocarbons (29.5%), and decreased in orders of ketones (6.8%), alcohol (2.3%), n-hexane (2.3%), and was highest in guitar painting (71.4%) workplace in case of aromatic hydrocarbons by component category.

• Journal of environmental and Sanitary engineering
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• v.13 no.3
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• pp.66-71
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• 1998

This study was investigated to evaluate worker exposures to organic solvents by type of print industry. Results were as follows; 1. Workers were exposed to mixture of toluene, isopropyl alcohol(IPA), methyl ethyl ketone(MEK), n-hexane, ethylacetate(EA), acetone. The components of high exposure solvents were toluene, IPA and MEK. 2. Considering additive effects of the compounds, exposure indices(Em) were calculated. The Mean of exposure indices were 1.79 for Gravere, 0.41 for Screen and 0.14 for Opset workplace. The workers of Gravere workplace were estimated to overexpose for solvents. 3. The highest overexposed solvent was toluene for a single component. The rate of overexposed level for toluene was 7.41% for some print workplace and for mixed solvent was 1.85％. 4. Local exhaust systems were inappropriate and respiratory protective devices were not supplied to the workers. 5. Sound level was over 90dB(A) in Opset print workplace and some measures should be performed to get down the sound level.