中学化学实验室管理初探

化学是一门研究物质组成、结构、性质、变化和合成规律的科学,始终得以物质为对象。所以,它具有鲜明.实验性的特点,即在化学教学过程中,师生必须从事一定的化学实验。而化学实验教学对于人才的培养又具有它特殊重要的作用,因为好的人才应该是知识、智力因素和非智力因素的有机总和。     

讨论初中化学第七章的教学——“最重要的几种酸、硷、氧化物和盐”

在初中化学课本第七章讨论到“重要的几种酸、硷、氧化物和盐”。通过前面六章教材的学习,使学生了解化学是研究物质及其变化的课程。根据物质构成的变化,去判定物质的转变;由分子及原子观点说明物质的结构;又对分子原子学说,基本的化学概念和定律等予以适当的讨论,也就是让学生把化学课程的基础理论部分,首先由感性到理性地建立起来。初中化学课本前六章的教材内容,还包括了空气、氧、氢、水和溶液,这是具有两种意义的;一方面因为这些教材是属于应用最广的物质,在初中化学中必须讲述,另一方面的意义是通过这     

水溶液中芘的荧光被核酸碱基猝灭的研究

众所周知,稠环芳烃是一类具有致癌性的物质.虽然对其致癌机理的认识尚未形成一致的看法,但一般都认为同稠环芳烃与DNA,蛋白质等生物活性物质的相互作用有关.因为致癌物后的致癌作用最终都是通过损伤细胞中的DNA而实现的.     

初中化学“物质和物质的变化、分子”的教学研究

一、本章在全部初中化学教材中的地位在绪言的教学里,学生已经初步地懂得了化学跟物理学、动植物学的区别。知道了化学是研究物质以及一些物质变成另一些物质的规律的科学。但这样的解释学生并不能一下子彻底接受,因为在学生的脑子里,对什么是物质和物质在怎样进行着变化的知识,还只是一些未经整理过的素材;他们常是把一些习见的变化,看成了不必解释的当然现象。曾经碰到过这样的事实:当你问学生蜡烛为什么一点就着时,他的回答是:“因为你用火去点它,所以它就着了”。当你再问他为什么一吹就灭时,他的回答是:“因为吹的风大,所以一定要灭”。这样的答案丝毫也不稀奇,因为他们还不懂得什么是物质,更不知道物质是什么构成的。当然也就不可能了解物质变化的本质了。要想让他们懂得这些变化的本质,先决的条件就是要解决物质构成的问题。其次还要认识物质的性质,因为不认识物质的结构和性质,就不可能看到它们所发生的变化。     

催化不对称合成

前言在生物体中,具有重要生理意义的有机化合物绝大多数都是具有旋光性的立体异构体。例如在生物体中普遍存在的α-氨基酸主要呈L-构型,由天然产物得到的单糖则多呈 D-构型。正因为生物体对某一物质的要求常严格地限定为某单一的构型,所以与生物物质有关的     

化合物中文俗名的釐订(上)

一、俗名的意义化学是研究物质间化学變化的学问。纯净的物质是元素或化合物。化合物的种類很多。僅就有机化合物而言,業已发现者约近一百萬种,而且数目还在日益增加。因为化合物     

贻贝中有机氯农药和多氯联苯标准物质的研制及同位素稀释高分辨质谱法定值

建立了贻贝中有机氯农药(OCPs)和多氯联苯(PCBs)标准物质的研制和定值方法,该研究对我国开展环境生物标准物质的研制具有重要的方法学借鉴价值。该标准物质样品为采自大连湾海域的贻贝,其定值目标物包括18种OCPs和16种PCBs,采用的定值测量方法是目前世界上最权威、最准确的同位素稀释-高分辨气相色谱/高分辨质谱联用法(ID-HRGC/HRMS)。所研制的标准物质具有定值目标物种类多、不确定度较小(约10%)等特点。该标准物质是目前国际上唯一一种采用同位素稀释高分辨质谱法进行定值的底栖生物中OCPs标准物质,于2012年3月通过了国家一级标准物质的终审,并于2012年6月被国家质量监督检验检疫总局批准为国家一级标准物质(GBW10069)。该标准物质可用于食品安全控制、环境监测、质量检测等领域相关分析方法的评价、测量质量控制及技术仲裁检验等。     

标准物质均匀性检验剖析

粉末混合物、矿石、合金等固体物质本身是不均匀的。因此,由这些物质制备的标准物质在分装成最小包装单元之后必须经过检验以评价均匀度。 均匀性,这一术语在ISO指南30:1992(E/F)《标准物质常用术语及定义》中是这样描述的:“对于物质的一种或多种指定特性具有相同结构或组分的一种状态。不论样品是否取自同一包装单元(如:瓶、包等),通过检验具有规定大小的样品,若被测定特     

硫化物和挥发性有机化合物对气相分子吸收光谱法测定水中亚硝酸盐氮含量的干扰和消除北大核心CSCD

气相分子吸收光谱法具有分析快速、维护费用低、所用试剂少等优点[1-3],已被广泛用于测定水中亚硝酸盐氮的含量[4-5],但该方法测定时会存在一定的干扰[6-7]。综合有关文献,干扰物质可分为两类:一类是具有氧化或还原性的物质,如MnO_(4)^(-)、I^(-)等,这些干扰物质是水中亚硝酸盐氮的共存物,影响体系的氧化还原平衡,不对气相分子吸收反应本身造成干扰,所以此类物质不作为干扰考虑;另一类是在反应体系和测定波长下生成有气相分子吸收的物质,如硫化物(S^(2-))、挥发性有机化合物(VOCs)等,这些物质可能会引人测定干扰,因此本工作主要针对S^(2-)和VOCs的干扰和消除开展研究。     

应用分子筛精制氩气

氩是一种与任何物质都不起作用的惰性气体。由于它具有这一特点,近代在各种工业与科学领域中应用日广,其中特别是对于金属的提炼与精制加工过程,如锑的高温精炼、高纯度金属及半导体的制备等都需要用到氩气。应该指出的是,这些过程不仅需要氩,而且需要纯度极高的氩,因为即使含有极微量的氧与氮,也将影响加工物品的质量与性能。     

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。     

Acid hydrolysis of carboxymethylcellulose of low degree of substitution

Cotton cellulose was swollen in a sodium hydroxide solution and carboxymethylated by a two-bath method for different periods of time for each process. The kinetics of acid hydrolysis and the crystallinity of the swollen and carboxymethylated samples were measured. The proportion of broken bonds, rate constants for hydrolysis, and permeability of cellulose to hydrolyzing agents were calculated. The susceptibility of glycosidic linkages to acid hydrolysis was improved by carboxymethylation more than by swelling in alkali. The increased accessibility of carboxymethylcellulose to acid was regarded as a consequence of increased intra-and intercrystalline swelling and of the glycosidic bonds' weakness caused by the electron-attracting carboxymethyl group on the C-6 position.     

Estimation of Kinetic Parameters of Thermal Oxidation of Ilmenite

The aim of the presented work was the investigation of thermal oxidation of ilmenite in static air atmosphere. The investigations were carried out by use of a derivatograph (MOM, Hungary). The changes of crystallographic structure of investigated samples were identified by X-ray diffractometry on Philips PW-1710 diffractometer. In temperature above 500°C appears structure of hematite Fe₂O₃. On the basis of the thermogravimetric measurements, the contracting area and contracting volume models were found as the best fitting experimental data. This revised version was published online in August 2006 with corrections to the Cover Date.     

Mechanism of action of base-catalyzed oxygenation of phenol derivatives

Cyclopropyl derivative of 2,6-di-tert-butylphenol is synthesized as a probe to investigate the mechanism of base-catalyzed autooxidation of phenol derivatives. Our study indicates that one electron reduction of molecular oxygen from phenolate gives phenoxyl radical 3, a key intermediate of autooxidation. The coupling of phenoxyl radical and superoxide radical gives peroxylate anion 4 and produces the final epoxy alcohol adduct 6.     

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^-。     

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.

     

化学计量中不确定度评定研究进展

测量不确定度是表征合理地赋予被测量之值的分散性的参数。本文针对化学计量不确定度评定基础模型仅适用于线性模型、概率分布为正态分布或缩放位移t分布等局限,介绍了近年来不确定度评定的研究热点:蒙特卡罗方法(Monte Carlo Method,MCM),不确定度评定的来源、评定概念、评估方法及其发展过程,扩大了测量不确定度评定与表示的适用范围。     

微量钙的测定方法研究进展

介绍了1995-2006年期间测定微量和痕量钙的方法,如电感耦合等离子体-原子发射光谱法、原子吸收光谱法以及离子色谱法等的工作原理和特点,并说明了其测定微量钙的应用领域。并对微量钙的测定技术进行了展望(引用文献55篇)。     

Stages of thermal decomposition of sodium oxo-salts of sulphur

Thermal behaviour of sodium oxo-salts of sulphur: Na₂SO₄, Na₂S₂O₇, Na₂S₂O₆, Na₂SO₃, Na₂S₂O₅, Na₂S₂O₄, Na₂S₂O₃, Na₂S₃O₆ and of sulphides Na₂S and Na₂S₂ was studied on heating up to 1000°C. The experiments were performed with anhydrous compounds obtained from commercial products by recrystallisation and dehydration. The stage mechanisms of decomposition of anionic sub-lattices of the salts have been proposed basing on the Górski’s morphological classification of simple species. The thermal stability and the stage decomposition mechanisms were correlated with the structure and the potential chemical properties of the salt anions. The thermal decomposition processes were studied by means of thermal analysis, and the decomposition products were identified by means of X-ray phase analysis.