仲钨酸A至仲钨酸B的转变动力学研究

在z(H~+/W)值0.35～1.10和温度70～85℃范围内,用H_2O_2-SO_2法测定了Na_2WO_4溶液中仲钨酸A转变成仲钨酸B的速率常数k。溶液接触玻璃表面积恒定时,k为零级反应常数,它与z值成反比,与单位体积溶液所接触的玻璃容器表而积成正比。玻璃容器表面的Si—O基对转变过程具有催化作用。z=1.00时的反应活化能为70.72kJ/mol。仲钨酸A转变成仲钨酸B的反应历程为化学吸附缩合机理。     

New Supramolecular Networks Based on Paratungstate with N-Donor Bridging Ligands

Three new supramolecular networks based on paratungstate and N-donor bridging ligands, [H₂bpmp]_2.5H[H₂W₁₂O₄₀]2H₂O(1), [H₂(bpp)]₂[H(py―CH₃)]_0.25[H(py―C₂H₅)]_0.25H_1.5[H₂W₁₂O₄₀]·4H₂O(2) and [H₂pip]₃[H₂W₁₂O₄₀](3)[bpmp=N,N'-bis(4-pyridylmethyl)piperazine; bpp=1,3-bis(4-pyridyl)propane; py=pyridine; pip=piperazine] were prepared by the hydrothermal synthesis and characterized by elemental analysis, infrared(IR), thermogravimetric(TG) analysis and single-crystal X-ray diffraction(XRD). All the compounds show high-dimen- sional supramolecular networks based on [H₂W₁₂O₄₀]^6- and the protonated N-donor ligands via the N―H···O―W hydrogen bonds and/or π···π stacking interactions. Their luminescent properties were investigated.     

单斜仲钨酸铵热分解的热化学测定

The heat of the thermal decomposition of monoclini c ammonium paratungstate, (NH4)10H2W12O42•4H2O, was measured in a HT-1000 microcalorimeter using three-step calorimetry and suitable thermochemical cycle. The standard enthalpy of the thermal decomposition reaction at 298.15 K and the standard enthalpy of formation at 298.15 K for monoclinic ammonium paratung-state were obtained to be (430.1± 10.2) kJ•mol－ 1 and－ (13 423.7±14.8) kJ•mol－ 1, respectively.     

仲钨酸铵的制备及研究

通过对比蒸发法与在蒸发法中添加晶种和钨酸铵溶液制备的仲钨酸铵产品,结果表明后者制备的晶形更完整、颗粒较粗,且是纯度更高的5水仲钨酸铵.对产品进行了X射线衍射分析与热重分析,并探讨了仲钨酸铵成核机制、动力学过程.最后讨论了添加晶种和钨酸铵溶液对晶体形貌的影响.     

单斜仲钨酸铵热分解的热化学测定

在钨的冶炼过程中,仲钨酸铵是必须的中间原料 .从溶液中结晶仲钨酸铵时,根据结晶条件的不同,可以得到不同类型的结晶 [1].一般在较低的温度时（低于 323 K）,得到三斜仲钨酸铵 (NH4)10H2W12O42· 10H2O,在较高温时（高于 323 K）,得单斜仲钨酸铵 (NH4)10H2W12O42· 4H2O.工业生产中,单斜仲钨酸铵是常见的产品 .仲钨酸铵的质量直接决定钨粉的质量,因此仲钨酸铵热力学性质对于控制其结晶条件及结晶的热分解条件具有重要的指导意义 .但迄今,很少有关于单斜仲钨酸铵的热力学性质的报导 .本文用双子型热导式微量热量计,根据单斜…     

Standard Enthalpy of Formation of Monoclinic Ammonium Paratungstate

Monoclinicammoniumparatlingstate,(NH.),,H,W,,O.,4H,O(s),isanessentialintermediatecompoundintheextractionoftungstenfromitsoresl.Theknowledgeofthepropertiesofammoniumparatungstateisdesirableforcontrollingitscrystallizationanditsthermaldecomposition.However,thestudyonthethermodynamicpropertieshasnotbeenreported.Inthepresentwork,theenthalpyofreactionforthethermaldecompositionofammoniumparatungstatewasmeasured,anditsstandardenthalpyofformationat298.15Kisobtained.Thesampleofmonoclinicanunoniumpa…     

A New Type of Amido-Substituted p-tert-Butylcalix

A convenient method for the synthesis of intramolecularly bridged calix[6]arenes by bis(chloroacetyl)amide was reported. A 1,3-singly bridged derivative and an asymmertical 1,3-4,5 doubly bridged derivative were obtained, respectively.     

新型成纤共聚酯

介绍了成纤共聚酯的研究工作主要是对聚对苯二甲酸乙二醇酯的研究、首先阐述了共聚单体的化学结构对共聚酯性能的影响。实验结果指出了经曲有限元 含有间）邻）位苯环结构和含柔性链结构的共聚是具有明显不同的物理例如,后者的玻璃化温度下降比前者大的多,前者的结昌速度减慢,而后乾的结晶速度加快。其次是阐述了共聚酯的物理性能对其纤维性能的影响,例如,玻璃化温度的降低有利于纤维染色性能的提高,含有柔性 的共聚酯玻璃化     

一类新型主体分子——杯冠化合物

本文综述了新型主体分子杯冠化合物的研究进展, 讨论了它们的合成、构象、手性性质、超分子识别功能以及作为化学传感器和模拟酶应用等方面的问题。     

仲钨酸A与仲钨酸B的化学活性及其转变速度的研究

根据ParaA和ParaB对H₂O₂反应活性的差异,提出己酸化的钨酸钠溶液经加热陈化后溶液中ParaB的测定方法(即H₂O₂-SO₂法)。求出不同Z(H⁺/W)值溶液在80℃时ParaB的形成速度,发现形成速度呈线性变化,且随Z值的增加而变慢。从ParaA和ParaB的结构解释了它们对H₂O₂活性上的差异。     

A New Ursene Type Triterpenoid from Crepis napifera

A new triterpenoid, urs-20-en-3β-acetoxy-22α-ol, and three known compounds 3β-acetoxy-amyrin, 3β-acetoxy-lupeol, lupeol were isolated from the leaves of Crepis napifera (Franch.) Babc. Their structures were determined by means of spectroscopic studies.     

一种新型低噪音碳纤维纳米电极

近年来,碳纤维超微电极在生命科学领域中已取得了广泛应用,电极的超微尺寸使之能对生物微环境进行实时监测^[1],还可作为微柱分离的检测 ^[2],自Adams研究组1976年开展微电极伏安法对细胞外液中生物胺以及有关代谢物的检测研究以来,碳纤维超微电极已成为探测脑内甚至单个细胞内神经递质的一种有力的工具,人们已对单个细胞内神经递质^[3]及激素^[4]的释放进行了探索性研究。     

A New Picrotoxane Type Sesquiterpene from Dendrobium densiflorum

A new picrotoxane type sesquiterpene named dendrodensiflorol has been isolated from the stems of Dendrobium densiflorum. Its structure was identified on the basis of spectroscopic method.     

四氢糠基丙二酸二乙酯的新法合成

四氢糠基丙二酸二乙酯的新法合成牛福水陈楠周智明＊（北京理工大学精细化工教研室１０００８１）四氢糠基丙二酸二乙酯是合成萘呋胺酯草酸盐的重要前体，而萘呋胺酯草酸盐做为一种新型周围血管扩张剂，对脑动脉硬化、脑血栓形成、脑栓塞、耳鸣、头颈损伤及其后遗症有良好...     

The Studies of A New Type of Crystalline Antimonic Acid

A new type of crystalline antimonic acid Sb2O5·3H2O was synthesized.The composition,crystal structure,the equilibrium distribution coefficients for sodium and potassium ions and the ion-exchange capacity of this exchanger were determined.With this exchanger,sodium inos were removed from potassium chloride,and the content of sodium chloride was reduced from 3.24% to 0.02%.Compared with other ion-exchange materials,the crystalline antimonic acid gives and unusual selectivity for potassium and sodium ions. The different compositions and properties of antimonic acid exchangers are obtained through different preparing conditions and its crystalline formula of Sb2O5·4H2O(C-SbA1) is currently accepted.This paper reports a new type of crystalline antimonic acid-Sb2O5·3H2O(C-SbA2),synthesized by an improved Kuzin′s method.Sodium ions are removed from potassium chloride with C-SbA2.The exchange efficiency is better than that of C-SbA1.