在线测定秦皮甲素和秦皮乙素水解反应速率常数的扫集-流动注射-芯片毛细管胶束电动色谱方法

建立了在线测定秦皮甲素和秦皮乙素水解反应速率常数的扫集-流动注射-胶束电动色谱新方法.该方法进样频率为12次/h,可在5 min内完全分离反应体系中的所有组分,30 min即可完成一个温度下的反应速率常数测定.由于该在线测定方法不需要终止水解反应,通过一次连续进样分析得到水解反应过程电泳谱图,从而可以获得水解反应过程中的一些信息.在最佳条件时,用0.1 mol/L KOH为催化剂,测得25,30,35,40和45C时秦皮甲素的水解反应速率常数分别为3.65×10-2/min、5.24× 10-2/min、7.12× 10-2/min、10.5×10-2/min和16.3×10-2/min,活化能为58.57 kJ/mol.用10 mmol/L KOH为催化剂,测得15,20,25,30和35℃时秦皮乙素的水解反应速率常数分别为2.26× 10-2/min,2.85× 10-2/min,3.55× 10-2/min,4.38× 10-2/min和5.29× 10-2/min,活化能为31.55 kJ/mol.     

运用溶度积计算平衡常数解答疑难问题

运用溶度积计算出与氢氧化镁沉淀相关的反应、与硫化铜沉淀相关的反应、与碳酸钙沉淀相关的反应的平衡常数。通过以上的计算与分析,让学生熟练掌握了运用溶度积计算化学平衡常数,从而判断反应能否发生。     

钙和镁的交流示波极谱连续滴定

钙和镁的测定一般采用络合滴定法,但终点不甚清晰,而且钙镁比例只允许为1:10-10:1,有的方法虽然提高比例到30倍,但不简便,干扰因素颇多。高鸿等对大量镁存在下钙的交流示波极谱滴定,解决了络合滴定中钙的测定问题。本文在此基础上讨论钙镁的连续滴定。在pH=10的含有0.1M氨液中,EGTA与Ca~(2+)、Zn~(2+)、Mg~(2+)络合的表观稳定常数分别为:logK’_(Ca-EGTA)=10.9;logK’_(Zn-EGTA)=8.2;logK’_(Mg-EGTA)=5.2。在含有1.0M氨液中,EGTA与Zn~(2+)的表观稳定常数为:logK’_(Zn-EGTA)=3.6,DCTA与Ca~(2+),Mg~(2+),Zn~(2+)络合的     

用镉离子电极电位滴定法测定镉、钙、镁

镉、钙、镁三种离子的混合物可根据它们与EDTA,EGTA所形成配位物稳定常数的不同,利用镉离子选择电极作指示,电位滴定法分别测定其含量。本文研究了三种组份测定的适宜条件,并对废水废液进行了测定,与常用方法相比较,结果一致。镉、钙、镁离子浓度在1.0×10~(-1)～1.0×10~(-4)M范围内均适用,相对误差≤±0.8%,变异系数≤0.9%。     

离子色谱法测定磷酸锂中微量的杂质元素

对离子色谱法测定磷酸锂中钾、钙、镁杂质离子的方法进行研究。采用DX-80型离子色谱仪,分离柱为Ion Pac CS12A-5μm阳离子分离柱,用2×10-2mol.L-1甲基磺酸溶液为淋洗液,流速为2 mL.min-1,测定了磷酸锂中各钾、钙、镁杂质离子的含量,相关系数分别为0.9996,0.9993,0.9994,相对标准偏差小于3%,样品回收率为98.1%~100.3%。     

MgCl2-KCl-NaCl-CaCl2熔盐电解镁机理

在725℃温度下,对MgCl2-KCl-NaCl-CaCl2熔盐体系进行电解.研究结果表明,镁电解过程中阴极过电压ηc只有12～51 mV,电解过程的过电压主要是由阳极引起的;阴极还原过程的极限扩散电流密度id为1.56 A/cm2;镁离子阴极放电反应的电子转移数为1.98;2个电子转移步骤之前存在着前置转化步骤MgCl+ Mg2++C1-.应用循环伏安法对4种不同配比下的镁离子行为进行的研究结果表明,CaCl2质量分数从10%增加到40%,维持MgCl2质量分数为10%以及NaCl与KCl的质量比为6: 1不变,随着CaCl2质量分数的增加,镁离子结合成不易移动的络合阴离子,镁离子迁移的电流分数减小,镁离子的析出电位从-1.595 V逐渐负移至与钙、钠共同沉积,阴极峰值电流Ipc值逐渐增大,阳极峰值电位与阴极峰值电位之差的绝对值|φpa-φpc|逐渐增大,阴极放电反应的可逆性逐渐降低.     

聚乙二醇-硫酸铵双水相萃取次甲基蓝的研究

利用分光光度法研究了次甲基蓝在聚乙二醇-硫酸铵双水相体系的萃取行为,探索了质量配比(mPEc/m(NH4)2SO4)、温度和次甲基蓝的浓度对双水相及次甲基蓝萃取率(Y)的影响.实验表明:(1)在一定的温度和浓度下,随着mPEC/m(NH4)2SO4的减小,分配系数K( cup/clow)增加,萃取率Y略有减小;(2)在一定的质量配比和浓度下,分配系数K(cup/clow)随温度的升高而增大,但萃取率Y却基本保持不变;(3)在一定的质量配比和温度下,随着次甲基蓝浓度的增加,分配系数K(cup/clow)增大;萃取率Y略有增加.在mPEG/m( NH4) 2SO4为1.50∶1,c次甲基蓝=8.915×10-5mol/L、t=30℃的实验条件下,K(cup/clow)=22.14,萃取率(y)可达95.43％.     

牛磺胆酸钠对胆红素与钙离子相互作用形成沉淀过程的影响的研究

本工作选择牛磺胆酸钠作为人体内胆汁酸盐的代表研究其对胆色素结石的重要成分——胆红素钙沉淀过程的影响。结果表明,牛磺胆酸钠的存在使胆红素钙沉淀的条件溶度积大大提高,并使沉淀反应速度大大减慢。在牛磺胆酸钠浓度较高的情况下,沉淀过程出现诱导期,说明牛磺胆酸钠在一定条件下可以抑制胆红素钙沉淀的形成。沉淀的红外光谱表明,牛磺胆酸并未结合在沉淀中,也未影响沉淀中胆红素与钙离子间的相互作用的部位。沉淀的扫描电镜观察结果经统计学处理表明牛磺胆酸钠的存在使沉淀的颗粒变小,颗粒的聚集程度减小。     

气相色谱法测定茄尼醇中有机溶剂残留量

建立了测定茄尼醇中甲醇、正已烷、乙腈残留量的气相色谱法.样品和对照品均以异丙醇为溶剂,四氢呋喃为内标物. 色谱柱HP-5MS石英毛细管柱(5%苯基硅氧烷-95%甲基聚硅氧烷,30 m×0.25 mm×0.25 μm);检测器FID. 程序升温方式:初温80 ℃,保持5 min,以8 ℃/min升温至120 ℃,保持10 min;汽化室温度200 ℃;进样口温度250 ℃;高纯N2气为载气,流速2.0 mL/min;进样量2 μL.     

重金属盐溶解-沉淀反应的吉布斯自由能变的定量估算

对重金属盐溶解-沉淀反应的吉布斯自由能变(ΔG)进行了定量估算;在不加缓冲剂和pH调节剂的纯水体系中,观测了重金属离子Pb2+、Ni 2+及Zn2+的沉淀-溶解反应,计算了反应的表观平衡常数Kf及表观溶度积常数K′sp;与此同时,对相关计算结果进行了实验验证.结果表明,重金属盐溶解-沉淀反应的ΔG只与反应物的初始浓度和平衡浓度有关,通过测定反应物的平衡浓度即可求得反应的ΔG;重金属离子Pb2+、Ni 2+及Zn2+的沉淀-溶解反应表观平衡常数Kf及表观溶度积常数K′sp皆随重金属盐的起始表观浓度Q0的增大而发生规律性变化:Kf先增大后减小,K′sp趋于最大恒定值,并接近于Ksp;而三种体系的ΔG均为负值,ΔG的绝对值先随Q0的增大而增大,然后趋于相对恒定.实验结果表明,不能用Kf而只能用Ksp描述重金属盐的沉淀-溶解平衡,ΔG绝对值与真正参与反应的反应物的量呈正相关;ΔG<0说明纯水中重金属盐的溶解反应是自发进行的.类似地,通过计算溶解-沉淀反应的ΔG,可以判断沉淀法处理重金属污染废水在热力学上的可行性.     

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^-。