环保型酸式自动滴定管的研制与应用

介绍了一种环保型酸式自动滴定管的结构、特点及使用方法。这种滴定管节省试剂，废液排放量极小，操作简单、省时，克服了常规微量滴定管精密度差、装液难、零点和滴定终点不易控制的缺点。通过数理统计方法，将环保型酸式自动滴定管与标称容量为50mL的常规酸式滴定管平行测定结果进行了比较，试验证明，该滴定分析的精密度、准确度不仅与50mL常规酸式滴定管相当，而且操作性还优于50mL常规酸式滴定管。     

自动电位滴定中滴定剂体积的光电计量法

在自动电位滴定中,分析仪器主要分为二类,一类是先预定好终点电位,然后在该电位时,仪器自动关闭电动滴定管阀。由于终点电位需要作出电位滴定曲线之后才能找出,故分析时操作不够简便。另一类分析仪器则可自动绘制出整个滴定过程的电位滴定曲线。制造这类仪器的主要困难是滴定剂的体积变化量难以转变成仪器所能方便接受的信号,目前是采用     

小型滴定管与小型滴定分析研究

微型化学实验 ( M.L)以其节约试剂经费、减少环境污染、提高实验教学质量等优点受到化学教育工作者的广泛重视 ,并在化学实验教学的某些学科中得到广泛应用。在滴定分析中 ,国内外有关的改革探索多是以微型方式进行的 [1 ]。我们认为有些微型化分析化学实验需要双管式微型滴定管和磁力搅拌器 ,初期投入较高 ,不符合通过微型化学实验节约教学经费的初衷。而用滴管、移液管、注射器改制的微量滴定管[2 ,3,4] 过于简陋 ,难以达到分析化学准确度、精密度的要求 ,基本操作方式改变较大 ,也难以达到师范院校的学生基本操作技能规范化的教学目标。…     

虹吸进液自动校准两用滴定管

本文设计了一种由一支常量滴定管、一支微量滴定管和校准管组成的连通器(图1),根据同一种液体在连通器里液面保持一定高度的原理,采用校准管来控制常量滴定管和微量滴定管内溶液的高度。操作溶液采用虹吸装置与连通器相联。这样,组成了一个可作常量滴定和微量滴定的装置,使用方便,也提高了分析精度。     

毛细滴管称量滴定法测定水中溶解氧

将微量称量滴定法应用于硫代硫酸钠-碘量法测定水中溶解氧的含量.在滴定中采用自制的聚乙烯毛细滴定管代替了国标GB 10738-1989中所规定使用的结构复杂精细的称量滴定装置.操作时,在聚乙烯毛细滴定管中吸满了Na2S2O3标准溶液,在精密电子天平上称得滴定前后(以淀粉为指示剂)毛细滴定管及滴定剂的总质量.从滴定中所耗Na2S2O3标准溶液的质量按文中所给出的公式即可计算水样中的溶解氧含量,所制作的毛细管滴定管每滴滴定剂的质量要求控制在0.005～0.010 g之间,滴定过程的相对偏差可控制在1.0%左右.由于滴定系在微量水平上进行,因此方法具有消耗试剂少,操作快速而方便,且能取得优于国标方法的准确度和精密度,对4个水样进行分析,测得结果的相对标准偏差值(n=7)在0.18%～0.66%之间,明显小于国标方法测定结果的相对标准偏差(0.43%～1.26%).     

航空润滑油酸植的测定

酸值是航空发动机润滑系统的一项重要指示 ,根据酸值的大小可以判断使用中润滑油的变质程度 ,对航空发动机运转状况进行动态监测 ,以便人们更换油料 ,从而保证机器不会由于油的原因而发生故障、损坏。酸值的测定 ,一般采用酸碱滴定法 ,即指示剂法和电位法判断终点 [1～ 4]。指示剂法是用中和乙醇为滴定溶剂 ,甲酚红作指示剂 ,用已知浓度的氢氧化钾乙醇溶液滴定 ,通过颜色的改变来指示终点 ;电位法则是用甲苯、水和异丙醇混合液作滴定溶剂 ,滴加已知浓度的氢氧化钾异丙醇溶液 ,以电位计读数对滴加体积作图 ,取曲线的突跃点为滴定终点。在测定…     

新型酸碱通用滴定器研制成功

西南石油学院化工系陈集等人研制了一种新型的酸碱通用滴定器。这种通用滴定器能迅速准确地加液调零,灵活自如地控制滴定过程,具有较高的精密度和准确度,克服了老式滴定管漏液、沾污、堵塞、终点液滴难以控制、加液调零     

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％。     

Antilg de／dt—E曲线上的示波极谱滴定法

在示波极谱滴定中,当去极剂切口位于示波极谱图|dE/dt|的最大值附近时,利用Antilg dE/dt～E示波图来指示滴定终点能使终点变化更为敏锐。原来较难进行滴定的一些体系现在可用这种方法滴定。在50Hz的交流电频率下,用氨羧络合剂滴定了Cd~(2+)、Pb~(2+)、Zn~(2+)、Co~(2+),滴定结果符合分析要求。非线性放大还可应用于以dE/dt～E示波图的扩张或收缩来指示滴定终点的示波极谱滴定法及以荧光电位线的伸长或收缩来指示滴定终点的示波电位滴定法,以提高终点变化的敏锐性。以亚硝酸钠滴定对氨基苯磺酸为例说明了这一方法的可行性。     

医药类专业基于滴定分析实验培养学生误差分析能力的教学设计

为提高医药类专业滴定分析化学实验教学效果,设计了一种新的滴定分析测定药品含量实验的教学模式,将实验设计成不同的条件实验,学生分别完成不同的条件实验后共享实验数据,通过处理实验数据,学生可以对整个实验进行条件分析,在学习滴定分析测定药物含量实验的过程中,对实验原理有更深的理解,提高了学生分析实验关键点和处理实验数据的能力,增强了团队合作意识。     

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。     

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.     

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.     

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.     

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.     

恶臭嗅辨实验室建设探讨

针对恶臭测试的环境影响问题,提出了解决的实例方案,并对方案的要点及优缺点进行讨论,此方案在实际操作中具有较好的效果。     

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^-。