排序方式: 共有18条查询结果,搜索用时 15 毫秒
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氧化藏红T褪色催化荧光法测定痕量钒 总被引:13,自引:3,他引:13
研究了在酸性介质中柠檬酸存在下,痕量钒(V)催化溴酸钾氧化藏红T的褪色反应及其动力学条件,建立了催化荧光测定痕量钒的新方法。催化反应在沸水浴中进行8min,为假零级反应,反应的表观活化能力为99.21kJ/mol,反应速度常数为0.12/s;该方法的检出限为2.2×10^-8g/L;线性范围为0.2 ̄2.4μg/L研究了共存离子的影响,用于人发和煤灰中痕量钒的测定,结果令人满意。 相似文献
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石蕊溶液在碱性溶液中变色不明显,这个问题虽小,但它一直困扰着我们的实验教学活动。利用手机软件颜色识别器、数字传感器等几种软硬件技术手段,对石蕊试剂的选择、配制方法的优化、溶液pH的调节等方面进行探究,试图配制出在酸碱性溶液中显色明显的石蕊溶液。 相似文献
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Thermal discoloration of cellulose (Avicel PH-101 and Whatman No. 42 filter paper) was studied in N2 at 160-280 °C with glycerol-treated and NaBH4-reduced samples, to understand the role of the reducing end. Thermal discoloration of glycerol-treated Avicel PH-101, in which some of the reducing ends were converted into glycosides (non-reducing ends), was suppressed compared with the original cellulose, and the level of suppression was directly related to the extent of glycosylation of the reducing ends. The stabilization efficiency of glycerol-treated Whatman No. 42 filter paper suggested that the reducing ends newly formed by reduction of the degree of polymerization (DP) (to about 200) during heat treatment contributed to the discoloration. The important role of the reducing ends in thermal discoloration was supported by the stabilization of Avicel PH-101 by reduction with NaBH4 (giving a reducing end content that was 2% of that of the original cellulose). Thermally induced discoloration was also inhibited by heating cellulose in suspension in the polyether tetraethyleneglycol dimethylether, which has been reported to inhibit the thermal degradation of reducing sugars. 相似文献
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根据加热通有二氧化碳的石蕊溶液未能恢复至紫色,揭示氯化氢与水形成恒沸溶液的本质,得到不能通过对溶液加热煮沸的方法除去氯化氢杂质的结论。 相似文献
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耐辐射致色聚烯烃的研究 总被引:2,自引:0,他引:2
研究了在γ射线辐照条件下受阻胺光稳定剂 (简称HALS)、各种抗氧剂对聚丙烯 (PP)和聚乙烯 (PE)的黄度 (YI)的影响。结果表明五甲基HALS比相应的四甲基HALS更能有效地阻止聚烯烃的辐射致色。抗氧剂Irganox 10 76比Irgafos16 8或IrganoxPS 80 2更有效。当抗氧剂和HALS并用时显示出协同效应 ,10 76和PDS并用时聚丙烯的黄度比单独添加 10 76或PDS的聚丙烯的黄度都低。 相似文献
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Sung Il Moon Chan Woo Lee Masatoshi Miyamoto Yoshiharu Kimura 《Journal of polymer science. Part A, Polymer chemistry》2000,38(9):1673-1679
Poly(L ‐lactic acid) (PLLA) was produced by the melt polycondensation of L ‐lactic acid. For the optimization of the reaction conditions, various catalyst systems were examined at different temperature and reaction times. It was discovered that Sn(II) catalysts activated by various proton acids can produce high molecular weight PLLA [weight‐average molecular weight (Mw ) ≥ 100,000] in a relatively short reaction time (≤15 h) compared with simple Sn(II)‐based catalysts (SnO, SnCl2 · 2H2O), which produce PLLA with an Mw of less than 30,000 after 20 h. The new catalyst system is also superior to the conventional systems in regard to racemization and discoloration of the resultant polymer. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1673–1679, 2000 相似文献
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