新课标下的氯气漂白性质的实验改进

为解决氯气漂白性质实验的繁琐和环境污染等问题,对该实验的装置、材料、演示方法进行了探讨,设计了在密闭的装置里进行实验的新方案,取得了良好的实验效果。     

密闭微波辅助萃取丹参中有效成分的研究

应用具有压力控制附件的MSP-100D密闭微波萃取装置,对丹参中的有效成分丹参酮、丹参酮A及隐丹参酮进行微波萃取研究.在乙醇体积分数为90%,微波辐射时间为4min,溶剂体积对样品质量比为20∶1和样品粒径为120目的条件下,有效成分提取率最佳.对比了密闭微波萃取同索氏萃取和超声萃取丹参有效成分的差异.     

气球在化学实验中的应用

一、在有关气体实验中的妙用（一）改进集气、洗气装置1. 装置如图1—4所示接入气球后改进的集气、洗气装置,具有下列优点：①可形成容积可变性密闭系统。具有一定的缓冲功能。②作尾气处理装置。     

硫在空气和氧气中燃烧实验的新探究

利用三口烧瓶、打火枪和恒压滴液漏斗等常见的实验仪器设计了一套实验装置,将硫在空气中的燃烧、氧气的制备、硫在氧气中的燃烧以及二氧化硫的吸收处理在一个密闭装置中完成,解决了教材中实验存在的不足。实验改进有利于培养学生的创新能力和环保意识,提高课堂的教学效果。     

高纯镓中微量硫的极谱测定

次甲基蓝光度法测定镓中硫,其分析下限只能达到4×10~(-5)％。原因是:检出灵敏度不够和空白值高。硫离子的极谱测定有足够的灵敏度,已用于砷、三氯化砷及其他纯物质中微量硫的分析。通常,空白值来源于试剂和环境玷污。本文提出一种还原剂兼作镓的溶剂,并使分析过程在完全密闭装置中进行。因而,试剂空白及环境玷污的机率均降至可忽略程度。仪器、设备、试剂     

一种ICP光源粉末进样装置

ICP光源固体粉末进样装置国内外均有报导,我们在吸取云南装置优点的基础上研制成一种ICP光源连续不断弧、密闭粉末进样装置。本装置具有进样均匀、稳定、不断弧、摄谱快、防护好。将该装置用于稀土矿样分析Y、Yb、La、Ce等元素,其相对偏差在4～19％范围内。     

氯气的制备与性质综合实验设计

将氯气制备与多个性质实验及尾气吸收综合在一起进行一体化创新设计,整个装置密闭,操作简单。该实验集微型化和综合性于一体,既节约试剂,现象明显,又可控速率,绿色环保,非常适合课堂演示。     

GC-MS技术在舰船复合板毒性评价中的应用

海军舰船舱室多为密闭环境,其舱室狭小,设备庞杂,人员密集。舱室内部的防护装饰多系非金属材料,随着现代各种复合、聚合材料的迅速发展和广泛使用,周围环境特别是密闭舱室空气污染的问题也更为突出。本文根据有关军用标准和规程[1],应用GC-MS技术对2种舰船复合板常温释放物和高     

卡尔费休滴定法测水简易装置的改进

用带橡皮塞的导管将滴定管的上口与锥形瓶连接构成一个密闭的滴定装置,将此装置应用于卡尔费休容量法测定水含量,在滴定过程中所有试剂与外界完全隔开,防止了滴定过程中空气中水蒸气的干扰．滴定终点明显,且能稳定8h以上。用该装置对甲醇样品中的水进行测定,回收率为100．4％～100．9％,测定结果的相对标准偏差小于0．25％。     

一种新的五日生物需氧量分析方法

利用荧光氧传感器连续监测封装在密闭培养皿中的废水溶氧浓度，提出了一种新的ＢＯＤ５分析方法，建立了两套ＢＯＤ５检测装置。实验结果表明，利用荧光氧传感器检测ＢＯＤ５，提高了测量的准确性和精度，可望成为新的标准化检测方法。     

Spatially restricted Double Z-Simplified Box Orbital basis sets: Optimization and comparison with some standard basis sets

As part of previous studies, we introduced a new type of basis function named Simplified Box Orbitals (SBOs) that belong to a class of spatially restricted functions which allow the zero differential overlap (ZDO) approximation to be applied with complete accuracy. The original SBOs and their Gaussian expansions SBO-3G form a minimal basis set, which was compared to the standard Slater-type orbital basis set (STO-3G). In the present paper, we have developed the SBO basis functions at double-zeta (DZ) level, and we have assessed the option of expanding the SBO-DZ as a combination of Gaussian functions. Finally, we have determined the quality of the new basis set by comparing the molecular properties calculated with SBO-nG with those achieved with some standard basis sets.     

Model studies of the optical rotation,and theoretical determination of its sign for β‐pinene and trans‐pinane

We have carried out extensive studies on the basis set dependence of the calculated specific optical rotation (OR) in molecules at the level of the time–dependent Hartree–Fock and density functional approximations. To reach the limits of the basis set saturation, we have devised an artificial model, the asymmetrically deformed (chiral) methane (CM) molecule. This small system permits to use basis sets which are prohibitively large for real chiral molecules and yet shows all the important features of the basis set dependence of the OR values. The convergence of the OR has been studied with n‐aug‐cc‐pVXZ basis sets of Dunning up to the 6–ζ. In a parallel series of calculations, we have used the recently developed large polarized (LPolX) basis sets. The relatively small LPolX sets have been shown to be competitive to very large n‐aug‐cc‐pVXZ basis sets. The conclusions reached in calculations of OR in CM concerning the usefulness of LPolX basis sets have been further tested on (S)‐methyloxirane and (S)‐fluoro‐oxirane. The smallest set of the LPolX family (LPol–ds) has been found to yield OR values of similar quality as those obtained with much larger Dunning's aug‐cc‐pVQZ basis set. These results have encouraged us to carry out the OR calculations with LPol–ds basis sets for systems as large as β‐pinene and trans‐pinane. In both cases, our calculations have lead to the correct sign of the OR value in these molecules. This makes the relatively small LPol–ds basis sets likely to be useful in OR calculations for large molecules. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

Efficiency of numerical basis sets for predicting the binding energies of hydrogen bonded complexes: evidence of small basis set superposition error compared to Gaussian basis sets

Binding energies of selected hydrogen bonded complexes have been calculated within the framework of density functional theory (DFT) method to discuss the efficiency of numerical basis sets implemented in the DFT code DMol3 in comparison with Gaussian basis sets. The corrections of basis set superposition error (BSSE) are evaluated by means of counterpoise method. Two kinds of different numerical basis sets in size are examined; the size of the one is comparable to Gaussian double zeta plus polarization function basis set (DNP), and that of the other is comparable to triple zeta plus double polarization functions basis set (TNDP). We have confirmed that the magnitudes of BSSE in these numerical basis sets are comparative to or smaller than those in Gaussian basis sets whose sizes are much larger than the corresponding numerical basis sets; the BSSE corrections in DNP are less than those in the Gaussian 6-311+G(3df,2pd) basis set, and those in TNDP are comparable to those in the substantially large scale Gaussian basis set aug-cc-pVTZ. The differences in counterpoise corrected binding energies between calculated using DNP and calculated using aug-cc-pVTZ are less than 9 kJ/mol for all of the complexes studied in the present work. The present results have shown that the cost effectiveness in the numerical basis sets in DMol3 is superior to that in Gaussian basis sets in terms of accuracy per computational cost.     

An augmented effective core potential basis set for the calculation of molecular polarizabilities

Calculations of molecular polarizabilities require basis sets capable of accurately describing the responses of the electrons to an external perturbation. Unfortunately, basis sets that yield suitable quantitative results have traditionally been all-electron sets with large numbers of primitives, making their use computationally intractable even for moderately sized systems. We present a systematic augmentation of the effective core potential basis set of Stevens et al. [J Chem Phys 81, 12 (1984), Can J Chem 70, 612 (1992)] for 39 main group elements based on the procedure used to construct diffuse and polarization functions in the well-known Sadlej basis sets [Collec Czech Chem Comm 53, 1995 (1988)]. Representative calculations have been performed and we have shown that results to within 1% of all-electron calculations using the Sadlej basis set can be obtained for <1-35% of the computational cost using this new basis set.     

Computational linear dependence in molecular electronic structure calculations using universal basis sets

Distributed universal even‐tempered basis sets have been developed over recent years that are capable of supporting Hartree–Fock energies to an accuracy approaching the sub‐μHartree level. These basis sets have also been exploited in correlation studies, in applications to polyatomic molecules, and in the calculation of electric properties, such as multipole moments, polarizabilities, and hyperpolarizabilities. Jorge and coworkers have also developed universal basis sets and have recently reported applications to diatomic molecular systems. In this article, we compare the molecular calculations reported by Jorge and coworkers with our previous studies. Particular attention is given to the degree of computational linear dependence associated with the various basis sets employed and the consequential effects of the accuracy of the calculated energies. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Minimal basis sets in calculations of intermolecular interaction energies

Several minimal (7, 3/3) Gaussian basis sets have been used to calculate the energies and some other properties of CH₄ and H₂O. Improved basis sets developed for these molecules have been extended to NH₃ and HF and employed to H₂CO and CH₃OH. Interaction energies between XH_n molecules have been calculated using the old and the new minimal basis sets. The results obtained with the new basis sets are comparable in accuracy to those calculated with significantly more extended basis sets involving polarization functions. Binding energies calculated using the counterpoise method are not much different for the new and the old minimal basis sets, and are likely to be more accurate than the results of much more extended calculations.     

Revised relativistic basis sets for the 5d elements Hf–Hg

The relativistic double-zeta (dz) and triple-zeta (tz) basis sets for the 5d elements Hf–Hg have been revised for consistency with the recently optimized 4f basis sets. The new dz basis sets have 24 s functions instead of 22 s functions, and the new tz basis sets have 30 s functions instead of 29 s functions. New contraction patterns have been determined, including the 6p orbital.     

The expansion of hydrogen states in Gaussian orbitals

The convergence properties of Gaussian orbitals are studied by considering a very simple system, the hydrogen atom. We have variationally optimized even-tempered basis sets containing up to 60 s functions for the ground state and the first excited S state of the hydrogen atom, to an accuracy of 10^–15E_h. In addition, we have freely optimized the exponents in basis sets containing up to 12 Gaussians. We have studied the convergence of the total energy, the kinetic energy, the extent of the atom as measured by r², and the Fermi-contact interaction at the nucleus in these basis sets as well as in basis sets augmented with additional diffuse or steep functions.     

Acetamide, a challenge to theory and experiment? On the molecular structure, conformation, potential to internal rotation of the methyl group and force fields of free acetamide as studied by quantum chemical calculations

The molecular geometry has been optimized without any constraints using different basis sets and levels of theory as: Hartree-Fock with basis sets 6–31+G**, 6–311++G**, cc-pVTZ and aug-cc-pVTZ, MP2 with basis sets 6–311++G** and cc-pVTZ, MP3 with basis set 6–311++G**, and density functional theory with basis sets 6–311++G** and cc-pVTZ. Small basis sets up to 6-31G predict the syn conformation of the methyl group to be the most stable conformation. Larger basis sets predict an unsymmetrical conformation with one of the H atoms perpendicular to the amide skeleton or an anti-like conformation. Dunnings correlation consistent polarized valence triple zeta, cc-pVTZ, basis set including MP2 predict two conformations, one perpendicular and one anti to be the most stable. The DFT calculations predict anti-like conformations. The most accurate calculations predict anti-like conformations which have not been predicted previously. The vibrational frequencies have been calculated for several basis sets and compared to the observed frequencies. The wagging frequency of the NH₂ is very dependent on the basis sets and levels of theory. Most calculations predict a planar NH₂ group in agreement with experiment. A scaled molecular force field has been determined by fitting the calculated frequencies to the observed ones for the perpendicular conformation using MP2/cc-pVTZ. The barrier heights for the methyl group have been calculated. The rotational constants, I_A + I_B − I_C values and dipole moments are compared with experimental values.