• Title/Summary/Keyword: aqueous hydrochloric acid system

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Nonlinear Regression Analysis of Acid-Base Titration System (산-염기 적정 시스템의 비선형 회귀분석에 관한 고찰)

  • Park, Chung-Oh;Hong, Jae-Jin
    • Korean Journal of Clinical Laboratory Science
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    • v.40 no.1
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    • pp.18-25
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    • 2008
  • In classical titrimetric analyses, the major concern is the concentration of titrant, usually the aqueous solution of hydrochloric acid or sodium hydroxide, that could be changed as time goes by and it is accompanied with the inaccuracy of the resulting data. And the statistical approach, the nonlinear regression analysis, which is a well-known statistical method, was introduced to determine the accurate concentration of the titrant and the exact value of parameters, $K_a$, r, $C_a$, $C_b$, for 0.01 M aqueous solutions of analytes, sodium pyruvate, sodium acetate, sodium bicarbonate, ammonium hydroxide, ammonium chloride and acetic acid at $25^{\circ}C$. We used Gauss-Newton method for the linearlization of the nonlinear titration system and the two-parameter fitting showed appreciable convergent data for the parameters of the analytes set with the various range of $K_a$ value.

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Chemical Factors on the Homogeneous Precipitation of Barium Titanyl Oxalate by Dimethyl Oxalate and Their Effects on the Charateristics of Barium Titanate (Dimethyl oxalate에 의한 barium titanyl oxalate의 균일 침전에 미치는 화학적 인자와 이들이 티탄산 바륨의 특성에 미치는 영향)

  • Ryu, Kyoungyoul;Huh, Wooyoung;Lee, Chul
    • Analytical Science and Technology
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    • v.12 no.3
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    • pp.230-234
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    • 1999
  • Barium titanyl oxalates (BTO) has been homogeneously prepared by thermal decomposition of dimethyl oxalate (DMO) in hydrochloric solution containing $Ba^{2+}$ and $Ti^{4+}$. Particles of BTO settled on the bottom of the beaker were collected at the aging time of 120 min using hydroxy propyl cellulose (HPC) as a dispersant. The reaction temperature, the concentration ratio of $[DMO]_0/([Ba^{2+}]_0+[Ti^{4+}]_0)$ and the existence of HPC were found to influence on morphologies of BTO, chemical yields and characteristics of barium titanates formed from their precursors.

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Enrichment of Lithium Isotopes by Cation Exchange Chromatography (양이온 교환 크로마토그래피에 의한 리튬 동위원소의 농축)

  • Kim, Dong Won;Kim, Chang Suck;Choi, Ki Young;Jeon, Young Shin;Jeong, Young Kyu;Park, Sung Up
    • Analytical Science and Technology
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    • v.7 no.2
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    • pp.201-204
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    • 1994
  • Cation exchange column chromatography of lithium was carried out to investigate the lithium isotope separation in aqueous ion exchange system. A Pyrex glass column of $50cm{\times}6mm$ inner radius with a water jacket was used as the separation column in experiment. Upon column chromatography using hydrochloric and succinic acid mixtures as an elunent, single separation factor, ${\alpha}$, 1.0068 was obtained. From the experiment, it was found that $^6Li$ was enriched in the resin phase and $^7Li$ in the solution phase.

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Clean and Efficient Synthesis of Furfural From Xylose by Microwave-Assisted Biphasic System using Bio-Based Heterogeneous Acid Catalysts

  • Vo, Anh Thi Hoang;Lee, Hong-shik;Kim, Sangyong;Cho, Jin Ku
    • Clean Technology
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    • v.22 no.4
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    • pp.250-257
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    • 2016
  • As an attempt to replacing petroleum-based chemicals with bio-based ones, synthesis of furfural from biomass-derived xylose attracts much attention in recent days. Conventionally, furfural from xylose has been produced via the utilization of highly corrosive, toxic, and environmentally unfriendly mineral acids such as sulfuric acid or hydrochloric acid. In this study, microwave-assisted biphasic reaction process in the presence of novel bio-based heterogeneous acid catalysts was developed for the eco-benign and effective synthesis of furfural from xylose. The microwave was irradiated for reaction acceleration and a biphasic system consisting of $H_2O$ : MIBK (1 : 2) was designed for continuous extraction of furfural into the organic phase in order to reduce the undesired side products formed by decomposition/condensation/oligomerization in the acidic aqueous phase. Moreover, sulfonated amorphous carbonaceous materials were prepared from wood powder, the most abundant lignocellulosic biomass. The prepared catalysts were characterized by FT-IR, XPS, BET, elemental analysis and they were used as bio-based heterogeneous acid catalysts for the dehydration of xylose into furfural more effectively. For further optimization, the effect of temperature, reaction time, water/organic solvent ratio, and substrate/catalyst ratio on the xylose conversion and furfural yield were investigated and 100% conversion of xylose and 74% yield of furfural was achieved within 5 h at $180^{\circ}C$. The bio-based heterogeneous acid catalysts could be used three times without any significant loss of activity. This greener protocol provides highly selective conversion of xylose to furfural as well as facile isolation of product and bio-based heterogeneous acid catalysts can alternate the environmentally-burdened mineral acids.