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131.
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133.
单扫描示波极谱法测定扑热息痛 总被引:2,自引:0,他引:2
扑热息痛与NaNO2在中性介质中发生反应,其亚硝化衍生物具有良好的电活性。在pH9.37的Britton-Robinson缓冲溶液中,于-0.56V(vs.SCE)产生灵敏的极谱还原峰,峰电流与扑热息痛质量浓度在0.007-0.4mg/L范围有良好的线性关系,检测下限为5μg/L。此法已用于测定小儿速效感冒灵。 相似文献
134.
研究了利用铝酸钠溶液碳酸化产生的沉淀, 经胶溶作用制备出纳米氢氧化铝溶胶的过程. 分析了铝酸钠溶液滴加到大量碳酸氢钠溶液中时发生的反应. X射线衍射研究结果表明, 在纳米氢氧化铝溶胶制备过程中, 从无定形氢氧化铝沉淀到拟薄水铝石的晶型转变过程是氢氧化铝沉淀胶溶时溶解再析出的过程. 将碳酸氢钠加入到苛性比为1.7的铝酸钠溶液中, 中和至苛性比为1.3后, 溶液诱导期中的紫外光谱显示270 nm处的Al(OH)3-6吸收增强. 经与含铝原子六配位的晶体紫外光谱对比后表明, 在铝酸钠分解生成氢氧化铝的过程中, 其铝的配位结构从四配位转化为六配位. 拟薄水铝石溶胶粒子的形貌与胶溶所用的酸和分散剂有关. 相似文献
135.
A chemiluminescence method for the determination of folic acid by the sodium hypochlorite–folic acid–semicarbazide hydrochloride system with a new flow injection technique has been established. The new method can perform simple, sensitive and rapid determinations of folic acid. The response to the concentration of folic acid, in the range of 1.0×10−75.0×10−5 g/ml, is linear. The relative standard deviation of the method is 2.3% (Cs=4.0×10−6 g/ml, n=11). The detection limit is 2.7×10−8 g/ml. This method is suitable for automatic and continuous analysis, and has been successfully tested for the determination of folic acid in a folic acid tablet. 相似文献
136.
A supported liquid and a poly(vinyl chloride) (PVC)-based membrane selective for dodecylsulfate (DS−) ion are described. The active element is a membrane containing a dissolved ion association complex of DS− with cetylpyridinium (CP+) cation. The supported liquid membrane electrode (acetophenone as solvent) showed a Nernstian response towards the DS− anion over the concentration range of sodium dodecylsulfate (SDS) from 8.3×10−3 to 1.0×10−6 mol dm−3 at 25 °C. The proposed electrode also showed a super-Nernstian potential response (108±2 mV decade−1) at low concentrations (1.0×10−9 to 1.0×10−6 mol dm−3). Moreover, this electrode showed good selectivity and precision (R.S.D.?2.0%), and was usable within the pH range 4.0-6.8. The proposed electrode revealed a lower limit of detection of 6.3×10−7 mol dm−3 and improved selectivity in comparison with the some previously reported DS− ion selective electrodes. The isothermal temperature coefficient of this electrode amounted to −0.001 V °C−1. The liquid membrane electrode may find application in the direct determination of SDS by the standard addition method at pH 5.0, and in the physicochemical studies of surfactant solutions. 相似文献
137.
多支链烷基苯磺酸钠水溶液的表面性质 总被引:5,自引:0,他引:5
用自制的四种高纯度多支链烷基苯磺酸钠,研究了支链结构对其表面性质的影响.结果表明,随支链烷基碳数增加,临界胶束浓度降低,标准吸附自由能DGadӨ更负;但是,饱和吸附量Γmax却随支链烷基碳数增加而减小,且临界胶束浓度时的表面张力γcmc随吸附量减小而降低,表现出与一般表面活性剂不同的变化趋势.从多支链烷基苯磺酸钠的分子结构特点,解释了随支链烷基碳数增加Γmax和γcmc的变化规律,探讨了分子的独占面积(as)对Γmax及γcmc的影响. 相似文献
138.
Joseph A. Rard Kirk J. Staggs S. Dan Day Susan A. Carroll 《Journal of solution chemistry》2006,35(8):1187-1215
Boiling temperature measurements have been made at ambient pressure for saturated ternary solutions of NaCl + KNO3 + H2O, NaNO3 + KNO3 + H2O, and NaCl + Ca(NO3)2 + H2O over the full composition range, along with those of the single salt systems. Boiling temperatures were also measured for the four component NaCl + NaNO3 + KNO3 + H2O and five component NaCl + NaNO3 + KNO3 + Ca(NO3)2 + H2O mixtures, where the solute mole fraction of Ca(NO3)2, x{Ca(NO3)2}, was varied between 0 and 0.25. The maximum boiling temperature found for the NaCl + KNO3 + H2O system is ≈134.9 ∘C; for the NaNO3 + KNO3 + H2O system is ≈165.1 ∘C at x(NaNO3) ≈ 0.46 and x(KNO3) ≈ 0.54; and for the NaCl + Ca(NO3)2 + H2O system is 164.7 ± 0.6 ∘C at x{NaCl} ≈ 0.25 and x{Ca(NO3)2} ≈ 0.75. The NaCl + NaNO3 + KNO3 + Ca(NO3)2 + H2O system forms molten salts below their maximum boiling temperatures and the temperatures corresponding to the cessation of boiling (dry-out temperatures) of these liquid mixtures were determined. These dry-out temperatures range from ≈300 ∘C when x{Ca(NO3)2} = 0 to ≥ 400 ∘C when x{Ca(NO3)2} = 0.20 and 0.25. Mutual deliquescence/efflorescence relative humidity (MDRH/MERH) measurements were also made for the NaNO3 + KNO3 and NaCl + NaNO3 + KNO3 salt mixture from 120 to 180 ∘C at ambient pressure. The NaNO3 + KNO3 salt mixture has a MDRH of 26.4% at 120 ∘C and 20.0% at 150 ∘C. This salt mixture also absorbs water at 180 ∘C, which is higher than expected from the boiling temperature experiments. The NaCl + NaNO3 + KNO3 salt mixture was found to have a MDRH of 25.9% at 120 ∘C and 10.5% at 180 ∘C. The investigated mixture compositions correspond to some of the major mineral assemblages that are predicted to control brine composition due to the deliquescence of salts formed in dust deposited on waste canisters in the proposed nuclear repository at Yucca Mountain, Nevada. 相似文献
139.
Wojciech Dmowski Jolanta Ignatowska Krystyna Piasecka-Maciejewska 《Journal of fluorine chemistry》2004,125(7):1147-1151
Sodium dithionite effectively promotes the addition of 1-bromo-1-chloro-2,2,2-trifluoroethane to the exocyclic double bond of β-pinene. The reaction proceeded in an MeCN/H2O system to give almost quantitatively a 1:1 mixture of diastereoisomers of 4-(2-bromoisopropyl)-1-(2-chloro-3,3,3-trifluoropropyl)-cyclohexene (1). Dehydrobromination of 1 with pyridine gave a mixture of regioisomeric dienes 2 and 3, while treatment with DBU at elevated temperature resulted in total dehydrohalogenation to give trienes 4 and 5. Reduction of 1 with Bu3SnH gave 1-(2-chloro-3,3,3-trifluoropropyl)-4-(isopropyl)cyclohexene (6) which on dehydrochlorination with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) afforded conjugated diene, 4-isopropyl-1-(trans-3,3,3-trifluoropropenyl)-cyclohexene (7), with 50% overall yield. All the transformations proceeded with the retention of configuration at the carbon atom C-4 and the final compound 7 exhibited high optical activity. 相似文献
140.
不同种类羧酸钠对草酸钙结晶过程中晶相的影响 总被引:2,自引:0,他引:2
采用X射线衍射法研究了水溶液中不同种类羧酸钠对尿结石主要成份草酸钙结晶的影响,这些羧酸钠分别为含有一、二、三和四个羧基的羟基乙酸钠(NaGly)、酒石酸钠(Na2Tart)、柠檬酸钠(Na3Cit)和EDTA二钠盐(Na2EDTA).结果表明,随着羧酸钠浓度的增加,草酸钙的晶相均发生规律性的变化:从最稳定的一水草酸钙(COM),到不稳定的二水草酸钙(COD),最后转化为次稳定的三水草酸钙(COT).不同结构羧酸钠抑制COM生长、促进COD生成的顺序为:Na3Cit >Na2Tart >Na2EDTA >NaGly.该结果将为临床上选择防结石药物提供新的思路. 相似文献