• Applied Chemistry for Engineering
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• v.17 no.2
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• pp.119-124
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• 2006

Natural organic matter (NOM) should be carefully considered in terms of its constituent and effect because NOM is complex substances that occur in spatially and seasonally varying concentrations in natural water. This review presents characteristics of natural organic matter present in water. These compounds mainly include humic substances, carbohydrates, proteins (amino acids), hexosamines, fats, oils, greases, and trace organic compounds (endocrine disrupting chemicals and pharmaceuticals and personal care products).

• Journal of the Korean Chemical Society
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• v.22 no.6
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• pp.423-430
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• 1978

The initiation mechanism of trioxane polymerization catalyzed by Ti$Cl_4$ in nitrobenzene was investigated. The kinetic studies revealed that the rate of polymerization was drastically decreased by the addition of a minute amount of water or methanol. A third substance as cocatalyst was not required for the polymerization. Measurements of dielectric constants gave no evidence for the zwitterionic mechanism of the polymerization. The electric conductivity measurements of polymerization system and the initiator solution showed that the initiation was started by Ti$Cl_3^+$ cation, formed by a disproportionation of the initiator in nitrobenzene.

• Journal of the Korean Chemical Society
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• v.38 no.6
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• pp.418-426
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• 1994

This study was aimed at the detection of 40 semi-volatile organic base/neutral compounds from soil among 129 priority pollutants listed by EPA. Two extraction procedures, sonication extraction and Soxhlet extraction, were studied as a extraction and concentration method for priority pollutants in soil. Extracts were analyted by GC/MS-SIM(selected ion monitoring). The analytical methods were tested by standard compounds spiked into blank soil. Accuracy and precision of the methods were measured by calculation of mean recovery and mean relative standard deviation. And the method detection limits were estimated.

• Journal of the Korean Chemical Society
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• v.22 no.4
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• pp.254-258
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• 1978

A simple and sensitive method of determining trace amounts of benzene hexachloride (BHC) in air has been investigated. The sample is passed through the n-hexane solution and the absorbance of it was measured at 245nm spectrophotometrically and the concentration of benzene hexachloride was calculated using a working curve obtained from the vaporized standard benzene hexachloride passed into n-hexane.

• Journal of the Korean Chemical Society
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• v.20 no.4
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• pp.277-279
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• 1976

A potentiometric titration method has been developed for the titration of copper with 2,5-dimercapo-1,3,4-thiadizole in aqueous solution using a silver electrode as an indicator electrode vs. the standard calomel electrode as a reference electrode. The 2,5-dimercapto-1,3,4-thiadiazole is very sensitive reagent for copper, which has been found to be highly selective for potentiometric determination of copper. Direct titration of trace amount of copper (0.02${\sim}$0.1 mg) is possible in the presence of a number of foreign ions in aqueous solution containing potassium hydrogen phthalate and sodium fluoride as masking agent under atmosphere.

• Journal of the Korean Chemical Society
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• v.18 no.2
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• pp.79-84
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• 1974

Adsorption isotherms of benzene and its derivatives on Spheron 6, a graphitized carbon black, are obtained using a sensitive quartz beam microbalance. From the isotherms the molecular area of each adsorbate on Spheron 6 is calculated on the basis of nitrogen area of 16.2 $A^2$. the results show that the molecules of each species are adsorbed on Spheron 6 with the planes of benzene rings lying flat on the surfaces and doing hindered rotation.

• Korean Journal of Materials Research
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• v.5 no.6
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• pp.709-709
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• 1995

원거리 플라즈마 화학증착법을 이용하여 저온에서 이산화규소박막을 제조하였다. 본 연구 에서는 공정변수인 기판의 온도, 반응기체의 조성 및 분압과 플라즈마 전력에 따른 산화막의 재료적인 물성을 평가하였다. XPS결과에서 산화막은 양론비(O/Si=2)보다 약간 적어 실리콘이 많이 함유된 막으로 나타났다. 이 경우 굴절율과 ESR분석에 의해 미결합된 실리콘의 양이 증가함을 알 수 있었다. SIMS분석에 의해 미량의 질소성분이 계면에 존재하는 것과 실리콘 미결함을 관찰하였다. FT-IR로부터 막내 수소량을 정량화하였으며 결합각 분포는 200℃이상에서 열산화막과 비슷한 값을 얻었다. 하지만 열산화막에 비해 높은 식각율을 보여 계면 스트레스에 의해 막내의 결합력이 약해진 것으로 생각된다.

• The Journal of Engineering Geology
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• v.10 no.2
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• pp.215-233
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• 2000

The national geochemical baseline mapping project has been conducted since 1996 to establish a quantitative assessment system for geochemical hazards in natural environments. The geochemical image maps have been edited for thirty-six elements(i.e., 10 major oxides and 26 trace elements) in light sediments, finer fraction than 150 $\mu$m, collected from first- to second-order streams(totally 11,000) over five provinces in the western half(ca. 45,000 km$^2$) of Korea. Natural background values of the elements were given for different geological environments. Based on the statistics, geochemical baselines were newly obtained for a quantitative hazard assessment on toxicity of heavy metals and deficiency of essential nutrients. Some chosen examples of geochemical hazards are presented based on new geochemical image maps and related baseline data.

• Journal of Science Education
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• v.34 no.2
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• pp.291-305
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• 2010

The aim of this study was to survey the perceptions of the elementary school teachers on the smallscale chemistry(SSC) following its training session. The teachers participating in the survey were 266 teachers in the Gyeongnam province. They were given a questionnaire that focused on the nine areas of the SSC: Needs for the teacher training and its application, its benefits, issues of safety and danger as well as treatment of environmental pollution, its economic efficiency and the development of investigative skills. The designed questionnaire was checked by an authority, and the responses to each question were tallied and analyzed. The results are as follows. The biggest problems of the traditional experimental methods as rated by the teachers were, in the order of importance, the preparation time, the legal liability of teachers for the safety and accidents, financial issues, disposal of the experimental wastes and the lack of relevant data. Since most of the teachers had not experienced the SSC lab programs in the field, they responded positively to the questions of need for its introduction and training. The implementation of the experimental SSC lab programs should proceed in the following order: introduction into the textbook, teacher training program, after-school education and the invitation of instructors. The most useful materials for the SSC program were CDs, videos, books and various printed materials, in that order. The responses regarding benefits of the SSC program included its simplicity, convenience, time savings, diversity, qualitative and quantitative aspects, integration into the regular class and use of toys. In particular, the teachers mentioned the increased safety due to the small amount of experimental reagents needed and the durability of plastic instruments. The familarity from the use of everyday tools as well as easy access to and the low-cost of the instruments were other important benefits. The teachers in general rated the educational content of the program highly, but many also found it to be average. Some pointed out the lack of sufficient discussion due to the individual or pair groupings as a potential shortcoming. The potential for development of problem solving ability and improvement of skills was rated positively. The number of teacher who rated the development of creativity positively was just over the half. As for the area of improving investigative skills, many found its assessment difficult and confusing because of the lack of its systemic definition and categorization. Based on the findings of this study, I would like to recommend the application and a wider dissemination of the small-scale chemistry lab program into the elementary school science curriculum.

• Economic and Environmental Geology
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• v.45 no.1
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• pp.9-21
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• 2012

In this study, we investigated the chemical characteristics of soils collected from the several deserts and loess in China known as the typical source areas of Asian dust (the Taklamakan desert, the Alashan desert, the Ordos desert and the Loess Plateau). Based on our analysis, we examined the possibility of adverse effects on environments and human health. In each desert and loess, major elemental compositions of soils did not show large variations, implying that the long-periodic mixing of soils in each area made their chemical compositions homogeneous. Minor elements of soils in each desert and loess showed more complicated patterns with strong correlations each other (e.g., Cr, Cu, As, Co, Ni, V, Y, Sc, Sn, Pb, Zn, Cd, Cs, Li, Th, U). These results thus enable us to discriminate the soil of the Loess Plateau from those of the other deserts in China. The results of sequential extraction experiments for soils showed that the chemical speciation of Fe was dominant in residual fraction (>85%) in all deserts and loess, but the fractions of Mn and Ca chemical speciations were very different in each area. In the case of Mn, the fraction of amorphous Fe-Mn hydroxides (55.4%) in the Central Loess Plateau and the carbonate fraction (33.8%) in Taklamakan desert were higher as much as 2 to 5 times than other deserts. The chemical speciations of Ca are dominant in carbonate fraction in Taklamakan (75.9%) and Alashan (50.5%) deserts, but carbonate fractions of Ca in the Loess Plateau and Ordos deserts were low (6.6% and 2.1%, respectively). According to the mobility of trace elements inferred from the results of sequential extraction procedure, we could classify them into five groups, and the mobility of Cd, Pb and Cu are more than 87%, 33% and 30%, respectively. Therefore, Cd, Pb and Cu in soils of deserts and loess could be easily dissolved when interacted with surface water. As such, they could give adverse effects on surficial environments and human health.