忽略第二级离解的判据推导和二元弱酸溶液氢离子浓度的近似计算*

为推导出忽略二元弱酸$H_{2}A$第二级离解的判据,设计了虚拟酸A和虚拟酸B并计算了酒石酸、虚拟酸A和虚拟酸B的准确氢离子浓度$[H^{+}]_{T}$和近似氢离子浓度$[H^{+}]_{AV}$。计算结果表明:忽略$H_{2}A$第二级离解的判据与$\frac{K_{a1}}{K_{a2}}$比值相关。从极端二元酸($K_{a1}=K_{a2}$)得到的判据为$\frac{2K_{a2}}{[H^{+}]_{AV}}为推导出忽略二元弱酸H_2A第二级离解的判据,设计了虚拟酸A和虚拟酸B并计算了酒石酸、虚拟酸A和虚拟酸B的准确氢离子浓度[H~+]_T和近似氢离子浓度[H~+]_(AV)。计算结果表明:忽略H_2A第二级离解的判据与■比值相关。从极端二元酸(K_(a1)=K_(a2))得到的判据为■,其中[H~+]_(AV)=■。■≤0.11判据具有广泛的普适性,可以用于所有二元弱酸溶液。新判据除了保证溶液氢离子浓度近似值[H~+]_(AV)的准确度外(误差SymbolqB@5%以内),同时还具有覆盖浓度区间宽的显著优点。     

数学方法推导一元弱酸溶液氢离子浓度的近似公式及适用条件

近似计算一元弱酸HA溶液的氢离子浓度[H+]（相对误差在±5%以内）是分析化学工作者需要掌握的方法。利用严谨的数学方法,获得了各类近似公式的使用条件和浓度适用范围。例如,从近似式[H+]AV1=1/2（-Ka+√Ka2+4cKa+4c）出发,推导出了计算氢离子浓度的其他2个近似公式：（1）c越小,[H+]AV1越趋向c。计算表明,当满足c≤1/19Ka和c≥5.0×10-7 mol/L时,弱酸HA就可作强酸处理,此时得到近似式[H+]AV4=c,这极大简化了弱酸溶液氢离子浓度的计算。（2）c越大,[H+]AV1越接近√cKa。当满足c≥105Ka和cKa≥10Kw时,弱酸溶液氢离子浓度可按最简式[H+]AV2=√cKa计算。还解释了c≥105Ka和c≤1/19Ka时所包含的物理意义。需要强调的是,本文首次给出了各近似式的浓度适用范围,比如忽略水的解离时,除了满足cKa≥10Kw,还必须要求c≥6.0×10-6 mol/L。     

主成分分析法-BP神经网络算法用于电位滴定法测定有机酸

采用电位滴定法测定混合液中3种以上的多元弱酸,主成分分析法处理了电位滴定的曲线数据,用BP神经网络进行有机酸预测计算。建立了滴定时滴定剂和混合液中有机酸浓度之间关系的模型,实现了不经分离直接测定溶液中几种小分子多元弱酸。结果表明:该神经网络计算出有机酸的预测值与实际值相对误差不大于5.0%。     

一元弱酸弱碱盐溶液中氢离子浓度的计算问题

无机化学中，关于弱酸弱碱盐溶液中氢离子浓度的计算公式，是以NH4Ac为例推导的，其公式为[1]:推导此公式的前提条件是Ka=kb，所以计算Ka与Kb相差不大的弱酸弱碱盐溶液中氢离子的浓度，无疑是可以的。如NH4AC：Kb=1.76×10（－5）；Kb=1．774×10（－5）。那么，对于Ka与Kb相差较大的弱酸弱碱盐，如NH4CN：Ka=4.93×10（－10）；Kb=1．774×10（－5），能否用此公式计算氢离子浓度呢？本文就此问题作如下讨论。一、计算一元弱酸弱碱盐溶液中氢离子浓度的精确公式以一元弱酸铵盐为例进行推导。设分子式为NH4A，在溶液中同时有NH4＋…     

一元弱酸溶液中氢离子浓度计算公式的使用条件

利用质子条件式（PBE）推导了一元弱酸溶液中氢离子浓度的各类计算公式，对它们的使用条件进行了解释。     

银纳米簇传感器应用于醋酸浓度的检测研究

本文基于pH调控的变色酸2R稳定的银纳米簇构建一个pH荧光传感器,尝试将该传感器应用于检测弱酸溶液浓度。通过一列的条件探究实验得到最佳检测条件。在最佳检测环境中,成功的实现了对醋酸溶液浓度的检测。检测结果与标示量非常接近,相对误差小,误差值在允许范围之内。良好的实验结果证明该pH荧光传感器用于检测弱酸溶液的浓度具有可行性和实用性。     

弱酸离解平衡的计算机辅助教学

弱酸离解平衡的计算机辅助教学王玲（武汉冶金科技大学１５３信箱４３００８１）关键词计算机弱酸离解离子强度缔合中图分类号Ｏ６１１．３近年来本人在教学中尝试利用电脑对教材中的弱酸离解平衡作定量计算，得到了有益的收获。在弱酸全稀释过程中，氢离子浓度单调变小在...     

关于一元酸准确滴定判据的商榷

化学分析教科书中给出的弱酸能被准确滴定的条件是cKa≥1.0×10-8。本文根据这一判据的来源(滴定突跃≥0.3pH单位),对一元酸体系的滴定情况进行了严格数学处理。计算结果表明,只有同时满足弱酸的浓度c1.0×10-3mol/L和cKa≥1.0×10-8条件下,弱酸才能被准确滴定。对于浓度极稀的酸溶液(c≤1.4×10-4mol/L),无论强酸还是弱酸都不能被准确滴定。对教材很少涉及的不同浓度酸碱互相滴定的情况也给出了有价值的结论。     

离子色谱法分离弱酸阴离子保留值规律的研究

 研究了离子色谱弱酸阴离子分析中以氢氧化钠作淋洗液时 ,弱酸阴离子的调整保留时间随淋洗液中氢氧化钠浓度变化的规律 ,建立了二者关系的非线性函数模型。将一元非线性问题转化为多元线性问题求解 ,磷酸根的调整保留值与淋洗液中氢氧化钠浓度关系回归方程的相关系数在 0 99以上。用该数学模型预测磷酸根阴离子的保留值 ,相对误差小于 5 % 。     

弱酸弱碱平衡的计算

在分析化学中常需进行有关酸碱平衡的计算,部分初学者对此感到困难。若采用“分配分数”概念进行运算,将使计算简化很多。下面以弱酸为例来说明这个问题。一、分配分数和其表示式弱酸在水溶液中因离解平衡而存有各级弱酸阴离子和酸分子,弱酸的总浓度为各种型式     

Dichroism of absorption and polarization of phosphorescence of molecules of the closed form of nitrobenzospirothiopyran

The spectral-polarization characteristics of absorption and phosphorescence of molecules of the initial form of nitro-substituted indolinospirobenzothiopyran were studied in oriented polyethylene films and in solutions with different polarity. An oscillator model of the electron transitions responsible for the formation of absorption and luminescence spectra was suggested. It was established that the principal differences in the spectral and photophysical properties of the compound studied and its oxygen-containing analog are associated with the fact that the electronegativity of the S atom is lower than that of the O atom. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1143–1146, June, 1997.     

非那雄胺合成工艺改进

非那雄胺能抑制5α-还原酶的活性,明显降低二氢睾酮水平,是一种治疗良性前列腺增生的有效药品。该合成工艺以甾烯酮酸为原料,将其与氯化亚砜反应,无须分离即与叔丁胺反应得17β-酰胺化合物,再氧化开环,环合,氢化,脱氢合成了非那雄胺。经元素分析、IR、1HNMR、13CNMR、MS分析表征了其结构。该法无须使用昂贵的2,2-二吡啶二硫化物和剧毒药品苯亚硒酸酐,且以乙酸铵代替氨气,降低了对设备的要求和腐蚀,更适用于工业生产。     

Determination of heats of detonation and influence of components of composite explosives on heats of detonation of high explosives

The heats of detonation of 20 simple high explosives and explosive mixtures were determined by means of an adiabatic detonation calorimeter designed by the authors. The results indicated that the performance of the instrument was reliable and the experimental data were very accurate. For explosive mixtures, there was a linear accumulative relationship between the heats of detonation of the explosive mixture and its components. Accordingly, the heats of detonation of explosive mixtures could be calculated directly from the heats of detonation of simple explosives and the characteristic heats of other components. The experiments showed that the gold or brass shell of the cylindrical charge could be substituted by a thick-walled porcelain shell, which had the advantage of cheapness.

     

Synthesis of phenolic components of Grains of Paradise

Two vanilloids, (5E)-8-(4-hydroxy-3-methoxyphenyl)oct-5-en-4-one (1) and 4-[3-hydroxydecyl]-2-methoxyphenol (2), isolated from the dried seeds of Grains of Paradise (Aframomum melegueta), were synthesized; the latter compound was made as the S-enantiomer and the material derived from the seeds was found to be a 1:1.7 mixture of the R and S isomers. The synthetic route used should allow the preparation of analogs having extended alkyl chains and consequently different lipophilicity, and 3, a homolog of 2, was also prepared.     

Summary of development of the theory of stability of colloids and thin films

In this review, the research of the author in the field of colloidal systems is summarized. The factors influencing colloidal stability are systematized and analyzed. Examples are presented to illustrate the practical utilization of the theory of stability of colloids and thin films.This review was prepared on the basis of the works of the author, which were awarded the State Premium for 1991 in the field of science and technology, chemistry section.Institute of Physical Chemistry, Russian Academy of Sciences, 117915 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1708–1717, August, 1992.     

Study of hydration of two cements of different strengths

Main hydration products of two cement pastes, i.e. CSH-gel, portlandite (P) (and specific surface S) were studied by static heating, and by SEM, TEM and XRD, as a function of cement strength (C-33 and C-43) hydration time (th) and subsequent hydration in water vapour.Total change in mass on hydration and air drying, M_o, increased with strength of cement paste and with hydration time. Content of water escaping at 110 to 220°C, defined as water bound with low energy, mainly interlayer and hydrate water, was independent on cement strength but its content increased with (th). Content of chemically bound (zeolitic) water in CSH-gel, escaping at 220-400°C, was slightly dependent on strength and increased with (th). It was possibly derived from the dehydroxylation of CSH-gel and AFm phase. Portlandite water, escaping at 400-500°C, was independent on cement strength and was higher on longer hydration. Large P crystals were formed in the weaker cement paste C-33. Smaller crystals were formed in C-43 but they increased with (th). Carbonate formated on contact with air (calcite, vaterite and aragonite), decomposed in cement at 600-700^oC. It was high in pastes C-33(1 month) and C-43(1 month), i.e. 5.7 and 3.3%, respectively; it was less than 1% after 6 hydration months (low sensitivity to carbonation) in agreement with the XRD study showing carbonates in the air dry paste (1month), and its absence on prolonged hydration (6 months) and on acetone treatment. Water vapour treatment of (6 months) pastes or wetting-drying increased this sensitivity.Nanosized P-crystals, detected by TEM, could contribute to the cement strength; carbonate was observed on the rims of gel clusters.This revised version was published online in November 2005 with corrections to the Cover Date.     

氯氧化镁生成热的研究

用氧化镁氯化镁水溶液制备了8水合氯氧化镁[nMg(OH)2·MgCl2·8H2O], 并测定了其在盐酸中的溶解热, 实验结果表明, 氯氧化镁溶解热与n值呈线性关系, 根据溶解热求出5Mg(OH)2·MgCl2·8H2O和3Mg(OH)2·MgCl2·8H2O的生成热分别为-7727.1和5888.1kJ·mol^1^-。     

Thermodynamics of the formation of oxosulfides of rare-earth elements

The enthalpies of solution of several oxosulfides of rare-earth elements and the high-temperature enthalpies of oxosulfides and oxosulfates of lanthanum and yttrium were measured using solution calorimetry and high-temperature microcalorimetry techniques. Standard enthalpies of formation and some thermodynamic properties of oxosulfides and oxosulfates were calculated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2 pp. 294–297, February, 1997.     

探究“铁的锈蚀条件”实验创新设计

设计了铁的锈蚀实验,说明了铁钉的处理方法,增加了温度、酸、碱的影响条件,实现了铁跟蒸馏水及空气中氧气快速反应而生锈,使实验在5 min左右就能够得到准确的结果。