对离子色谱法测定煤炭中氟和氯量中样品处理方法的比较

用离子色谱法测定煤炭中氟和氯含量,对样品的两种前处理方法(高温燃烧水解和氧弹燃烧法)的适用性进行比较。选取含氟及氯的煤标准物质,分别用上述两种前处理方法处理后,将所得试液用同样分析条件进行测定。结果表明:(1)氧弹燃烧法的检出限(3S/N)(F-0.036μg·g-1,Cl-0.099μg·g-1)低于高温燃烧水解法(F-0.072μg·g~(-1),Cl-0.198μg·g~(-1));(2)两种方法对氟、氯的测定结果均与标准物质的认定值相符,对氯测定结果的准确度和精密度较高,测定值与认定值之间的相对误差在-1.0%~1.0%之间;(3)对氟测定,氧弹法结果的准确性低于高温燃烧水解法,前者与认定值的相对误差在-6.5%~-4.0%之间,而后者与认定值的相对误差在0.36%~3.6%之间。但氧弹燃烧法不适用于灰分大于25%的煤样。     

卟啉化合物的热化学研究: V. 含溴卟啉化合物的标准燃烧能和生成焓

用本实验室建立的精密转动氧弹燃烧热量计测定了标准物质对溴苯甲酸、辅助物质鲨烷及四对溴苯基卟啉(Tp-BrPP)的标准燃烧能, 并计算出了它们的标准生成焓。     

卟啉化合物的热化学研究: V. 含溴卟啉化合物的标准燃烧能和生成焓

用本实验室建立的精密转动氧弹燃烧热量计测定了标准物质对溴苯甲酸、辅助物质鲨烷及四对溴苯基卟啉(Tp-BrPP)的标准燃烧能, 并计算出了它们的标准生成焓。     

氧弹燃烧灰化法测定有机物中氯

采用氧弹燃烧灰化法进行样品预处理,使有机物中的氯转化为氯离子,然后用AgNO3滴定法测定氯的含量Ⅲ。通过测定面粉、虾米以及固体卤代芳烃,结果表明,方法准确、重现性好,灵敏度高,回收率为97．5％～102％,可用于有机物中氯的测定。     

氧弹燃烧–自动电位滴定法测定助焊剂中的卤素

建立氧弹燃烧–自动电位滴定法测定助焊剂中卤素的分析方法。在氧弹罐加入20 mL 0.25 mol/L氢氧化钠溶液作为吸收液,通过氧弹罐燃烧使得助焊剂中共价态的卤素转变成为离子态,利用氢氧化钠溶液吸收氧弹燃烧所释放的离子态卤素,吸收后的溶液用硝酸溶液(1∶1)进行酸化,消除碳酸根、碳酸氢根、氢氧根离子的干扰。处理后的样品溶液用0.01 mol/L硝酸银标准溶液进行滴定。助焊剂样品中卤素测定结果的相对标准偏差为0.51%～3.24%(n=5),加标回收率为95.24%～100.49%。该方法样品处理简单,操作简便,成本低廉。     

卟啉化合物的热化学研究——Ⅴ.含溴卟啉化合物的标准燃烧能和生成焓

用本实验室建立的精密转动氧弹燃烧热量计测定了标准物质对溴苯甲酸、辅助物质鲨烷及四对溴苯基卟啉(T_(p-Br)PP)的标准燃烧能,并计算出了它们的标准生成焓。     

氧弹燃烧–原子荧光光谱法测定煤中汞含量

建立氧弹燃烧–原子荧光光谱法测定煤中汞含量的方法。用氧弹燃烧分解样品,汞释放后以硝酸溶液吸收,以0.5 g/L硼氢化钾溶液作为还原剂,体积分数5%的硝酸溶液为载流液,用原子荧光光谱法定量测定。方法检出限为0.02μg/kg,对标准物质GBW 11156(标准值0.32μg/g)进行平行测定,测定结果的平均值为0.318μg/g,相对标准偏差为7.3%(n=6),加标回收率为91.5%~106.5%。该方法简单、干扰少,准确度和精密度良好,可用于煤中汞的测定。     

氧弹燃烧-离子选择性电极法测定氟

介绍了一种测定试样中氟含量的快速方法。首先利用氧弹燃烧技术对样品进行预处理,将氟转化为氟化氢,用碱液吸收燃烧产物,吸收液加入TISAB消除Al^3 、Fe^3 等离子干扰,调节溶液pH在5～8后进行定容,然后用氟离子选择性电极用标准加入法测定溶液的电位,从而测得样品中氟的含量。对香烟、头发和饲料进行分析,结果表明该法简单、快速、结果可靠,可用于试样中氟的快速测定     

2-氯丁烷、1,2=二氯丁烷气态生成焓的测量

用转动氧弹燃烧热量计测量了298.15K时2-氯丁烷和1,2-二氯丁烷的标准液态燃烧反应内能变化值,得到了它们的标准所态生成焓值,并进一步考查了二氯取代地氯代烷烃气态生成焓值的影响量.     

三聚氰胺的生成焓、热容和熵

通过多种热化学方法研究了三聚氰胺的热力学性质. 首先用氧弹式燃烧热量计测定了三聚氰胺在298.15 K 时的燃烧热, 根据燃烧热结果, 计算出三聚氰胺的标准摩尔燃烧焓和标准摩尔生成焓, 分别为: △cHΘm=(-2455.17±4.65) kJ·mol-1; △fHΘm =(-763.38±5.16) kJ·mol-1. 然后根据键焓与燃烧焓之间的关系, 估算出三聚氰胺中的C≈N(此键介于单键与双键之间)键能为458.30 kJ·mol-1, 此值介于碳氮单键键能和双键键能之间. 通过绝热热量计测定了三聚氰胺从80到385 K的低温热容. 根据热容值, 计算了此温度区间的标准摩尔生成焓, 其与温度呈线性关系. 另外, 三聚氰胺的热稳定性也用热重-差示扫描量热(TG-DSC)法进行了分析, 确定其分解的DSC曲线的峰顶温度为603.37 K.     

The enthalpy of formation of fullerene fluoride C<Subscript>60</Subscript>F<Subscript>18</Subscript> and the C-F bond energy

The enthalpy of combustion of crystalline fullerene fluoride C₆₀F₁₈ was determined in an isoperibolic calorimeter with a rotating platinized bomb, and the enthalpy of formation of the compound was calculated. The enthalpy of sublimation of C₆₀F₁₈ measured earlier was used to calculate the enthalpy of formation of fullerene fluoride in the gas phase and the mean enthalpy of dissociation of C-F bonds in this compound.     

Oxygen bomb combustion of biological samples for inductively coupled plasma optical emission spectrometry

A rapid sample preparation method is proposed for decomposition of milk powder, corn bran, bovine and fish tissues, containing certified contents of the analytes. The procedure involves sample combustion in a commercial stainless steel oxygen bomb operating at 25 bar. Most of the samples were decomposed within 5 min. Diluted nitric acid or water-soluble tertiary amines 10% v/v were used as absorption solutions. Calcium, Cu, K, Mg, Na, P, S and Zn were recovered with the bomb washings and determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Ethanol mixed with paraffin was used as a combustion aid to allow complete combustion. A cooling step prior releasing of the bomb valve was employed to increase the efficiency of sample combustion. Iodine was also determined in milk samples spiked with potassium iodide to evaluate the volatilization and collection of iodine in amine CFA-C medium and the feasibility of its determination by ICP-OES with axial view configuration. Most of the element recoveries in the samples were between 91 and 105% and the certified and found contents exhibited a fair agreement at a 95% confidence level.     

Low‐Temperature Heat Capacities and Standard Molar Enthalpy of Formation of Gramine (C11H14N2)

Low‐temperature heat capacities of gramine (C₁₁H₁₄N₂) were measured by a precision automated adiabatic calorimeter over the temperature range from 78 to 401 K. A polynomial equation of heat capacities as a function of temperature was fitted by least squares method. Based on the fitted polynomial, the smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15 K were calculated and tabulated at 5 K intervals. The constant‐volume energy of combustion of the compound at T=298.15 K was measured by a precision oxygen‐bomb combustion calorimeter as Δ_cU=−(35336.7±13.9) J·g⁻¹. The standard molar enthalpy of combustion of the compound was determined to be Δ_cH_m⁰=−(6163.2±2.4) kJ·mol⁻¹, according to the definition of combustion enthalpy. Finally, the standard molar enthalpy of formation of the compound was calculated to be Δ;_cH_m⁰=−(166.2±2.8) kJ·mol⁻¹ in accordance with Hess law.     

二甲氧基嘧啶胺与金属配合物的恒容燃烧热测定

在无水乙醇中，使钴、铜、锌、锰的盐与二甲氧基嘧啶胺(AMP)反应，回流数 小时后，浓缩、冷却，抽滤，制得了6种二甲氧基嘧啶胺与钴、铜、锌、锰的固态 配合物．用化学分析和元素分析确定了它们的组成，分别为Co(AMP)_2Cl_2(1)， Cu(AMP)_2Cl_2(2)，Cu(AMP)_2(NO_3)_2(3)，Zn(AMP)_2Cl_2(4)，Mn(AMP) _2Cl_2(5)和zn(AMP)s04(6)；用IR，～1H NMR研究了他们的成键情况；用精密转动 弹热量计测定了配体及配合物的恒容燃烧热△_cU，计算了它们的标准摩尔燃烧焓 △_cH_m～θ和标准摩尔生成焓△fH_m～θ．     

氧弹燃烧-离子色谱法测定煤中氯含量

建立了氧弹燃烧-离子色谱测定煤中氯含量的方法.在加有(NH4)2CO3溶液和过量氧气的氧弹中燃烧煤样,释放的氯被(NH4)2CO3溶液吸收,过滤溶液后, 采用离子色谱外标法测定滤液中氯的浓度,最后计算出煤中氯的含量.色谱工作条件:淋洗液为1.8 mmol/L Na2CO3与1.7 mmol/L NaHCO3混合液,流速1 mL/min;再生液为40 mmol/L H2SO4,流速0.5 mL/min;进样量20 μL.色谱标准工作曲线线性相关系数0.9996;10次测定1 mg/L Cl-标准溶液的均值为1.0012 mg/L,相对标准偏差为1.34%;8个煤样加标回收率为90.7%～104.3%;测定标准物质GBW11119 及GBW11120的相对误差分别为1.75%和1.36%;对比研究显示,氧弹燃烧-离子色谱测定8个煤样(除两个煤样外)氯含量结果远高于艾士卡剂混合熔样-离子色谱测定结果,表明艾士卡剂混合熔样过程由于煤样未处于完全密闭状态导致部分氯的散失.     

Calorimetric and computational study of 1,4-dithiacyclohexane 1,1-dioxide (1,4-dithiane sulfone)

This work reports the enthalpies of formation in the condensed and gas state of 1,4-dithiacyclohexane 1,1-dioxide (1,4-dithiane sulfone, 5), derived from the enthalpy of combustion in oxygen, measured by a rotating bomb calorimeter and the variation of vapor pressures with temperatures determined by the Knudsen effusion technique. The theoretically estimated enthalpy of formation was calculated from high-level ab initio molecular orbital calculations at the G2(MP2) level. The theoretical calculations appear to be in very good agreement with experiment. A comparison of the conversion of thiane sulfone 3 to 1,3-dithiane sulfone 4 and 1,4-dithiane sulfone 5 clearly shows the 1,3 isomer to be 6.7 kJ mol(-1) less stable, probably owing to diminished electrostatic repulsion between the sulfur heteroatoms in 1,4-sulfone 5.     

The standard enthalpy of formation and low-temperature heat capacity of 1,1′,3,3′-tetra-(<Emphasis Type="Italic">tert</Emphasis>-butyl)ferrocene

The heat capacity of crystalline 1,1′,3,3′-tetra-(tert-butyl)ferrocene (TTBF) was measured in an adiabatic vacuum calorimeter over the temperature range 5–302 K. The thermodynamic functions of TTBF in the crystalline state were calculated from T→0 to 302 K. The enthalpy of combustion of TTBF was determined in an isothermal calorimeter with a stationary bomb. The standard thermodynamic functions of formation of the compound in the crystalline state at 298.15 K were calculated.     

The thermodynamic properties of <Emphasis Type="Italic">bis</Emphasis>-(η<Superscript>5</Superscript>-cyclopentadienylirondicarbonyl)

The temperature dependence of the heat capacity of crystalline bis-(η⁵-cyclopentadienylirondicarbonyl) was studied over the temperature range 5–495 K in precision adiabatic vacuum and differential scanning calorimeters. The temperature dependence contained an anomaly (160–295 K) with a maximum at 250 K interpreted as a λ transition in the solid state. The fusion of the sample occurred at 435–491 K; it was accompanied by partial substance decomposition. The thermodynamic functions of crystalline bis-(η⁵-cyclopentadienylirondicarbonyl) were calculated from T→0 to 472.9 K. The enthalpy of combustion of the compound was determined in an isothermal calorimeter with a stationary bomb. The standard thermodynamic functions of its formation in the crystalline state at 298.15 K were calculated.     

Thermochemistry of 2-amino-3-quinoxalinecarbonitrile-1,4-dioxide. Evaluation of the mean dissociation enthalpy of the (N-O) bond

The standard enthalpy of formation of the 2-amino-3-quinoxalinecarbonitrile-1,4-dioxide compound in the gas-phase was derived from the enthalpies of combustion of the crystalline solid measured by static bomb combustion calorimetry and its enthalpy of sublimation determined by Knudsen mass-loss effusion at T= 298.15 K. This value is (383.8 +/- 5.4) kJ mol(-1) and was subsequently combined with the experimental gas-phase enthalpy of formation of atomic oxygen and with the computed gas-phase enthalpy of formation of 2-amino-3-quinoxalinecarbonitrile, (382.0 +/- 6.3) kJ mol(-1), in order to estimate the mean (N-O) bond dissociation enthalpy in the gas-phase of 2-amino-3-quinoxalinecarbonitrile-1,4-dioxide. The result obtained is (248.3 +/- 8.3) kJ mol(-1), which is in excellent agreement with the B3LYP/6-311+G(2d,2p)//B3LYP/6-31G(d) computed value.