2-(3,5-二溴-2-吡啶偶氮)-5-二乙氨基苯酚作络合滴定指示剂连续测定铁和铝

对2-(3,5-二溴-2-吡啶偶氮)-5-二乙氨基苯酚作铁(Ⅲ),铜(Ⅱ)的配位滴定指示剂进行了研究.在pH1.8～2.0时用EDTA标准溶液滴定铁(Ⅲ).在滴定铁(Ⅲ)后的溶液中,加入对铝过量的EDTA标准溶液,在pH3.8～4.0煮沸下,铝(Ⅲ)与EDTA生成稳定的络合物,过量的EDTA用硫酸铜标准溶液滴定,从而测定铝(Ⅲ).     

抗坏血酸容量法测定铁矿中全铁

抗坏血酸遇光受热等均能被氧化,稀溶液更不稳定,致使直接滴定铁的方法难以应用。来自蒸馏水中的微量铜对抗坏血酸被氧化有催化作用,但加入少量EDTA,能抑制这一效应,大大改善标准溶液的稳定性,从而使该方法简便、快速、准确、可靠。 1 试剂 抗坏血酸标准溶液:0.04mol·L~(-1),抗坏血酸(分析纯)3.34g溶于300ml水中,加EDTA(0.01mol·L~(-1))5.1ml,稀至1L,贮于深色塑料瓶中,避光存放阴凉处(每次测定试样时,用铁标准溶液(2mg·ml~(-1))标定抗坏血酸标准溶液的滴定度)。 2 分析方法 视含铁量称取试样0.1000～0.2000g。置于50ml聚四氟乙烯坩埚中,加水润湿,加入高氯酸1ml,氢氟酸5ml,低温加热,直到高氯酸白烟冒尽,驱赶多余的氢氟酸和四氟化硅的同时,使铁全部氧化至高价,加入盐酸(1 1)5ml,温热提取,将坩埚内溶物定量转移到     

返滴定法测定牛磺酸钙中的钙

测定合成牛磺酸钙 (Ca(NH2 CH2 CH2 SO3) 2 )中的钙含量 ,常采用在 p H1 0的氨 -氯化铵缓冲溶液中用铬黑 T作指示剂、EDTA标准溶液直接滴定的方法。终点附近溶液颜色变化不明显 ,难以判断 ,造成很大的分析误差。试验过程中观察到牛磺酸钙中加入铬黑 T指示剂后经数分钟才逐渐变色。初步推测可能是牛磺酸根对钙离子有一定的配位作用 ,使 EDTA测定钙的稳定常数减小 ,导致滴定突跃范围缩小 ,终点颜色变化不敏锐。为此 ,改用返滴定法。首先加入过量 EDTA标准溶液 ,加热反应后 ,再用过量的 Zn2 +标准溶液滴定剩余的EDTA,终点由蓝色变…     

矿石中铅锌快速络合滴定法

利用铅锌矿中铅生成复盐沉淀 ,用EDTA标准溶液滴定锌 ,然后溶解复盐沉淀 ,加入过量EDTA标准溶液 ,用硝酸铅标准溶液反滴定。利用本方法测定铅锌矿中铅、锌 ,其铅的检测范围为质量分数 0 .4%～ 2 5 % ,锌的检测范围为质量分数 >1 % ,能满足地质检验中的分析误差要求。     

甲烷生物催化氧化制甲醇——几种化学物质对Methylosinus trichosporium 3011甲醇累积的影响

本文报导了在 Methylosinus trichosporium 3011细胞反应液中加入一些化学物质对甲醇累积的影响。结果表明,Na~+抑制甲烷单加氧酶的活性。当 M.trichosporium 3011细胞反应液中含高浓度磷酸根时,只有很少量甲醇累积下来。EDTA 和 Na_2EDTA 甲醇累积的促进作用小于甲酸钠或甲酸的作用。但由于 EDTA 不仅可以抑制甲醇脱氢酶的活性,而且可以螯合 Na~+,而甲酸则可使 NADH 辅酶再生。因此,反应液中含有2mM EDTA 和20mM 甲酸时甲醇累积量最高。     

铅锡合金中锡和铅的连续示波滴定

报道了铅锡合金中铅、锡含量的连续示波测定方法 ,选择在pH 5 .5的缓冲介质中 ,以NH4F释放Sn EDTA中的EDTA和 (NH4) 2 MoO4释放Pb EDTA中的EDTA ,采用Zn2 +标准溶液滴定。方法快速简便 ,终点直观 ,标准加入回收率在99.5 %～ 1 0 0 .5 %之间 ,RSD <0 .5 %     

络合滴定法测定硅铁中铝含量的改进

络合滴定法测定硅铁中铝量,GB4333.5—84中用甲基异丁基酮将铁萃取后,用硫酸铜标准溶液滴定过量的EDTA,加入氟化钠释放与铝络合的EDTA,再用硫酸铜标准溶液回滴,由于该法操作条件严格,费时,不能适用于一般中小企业生产控制要求.本文在试样以硝酸、氢氟酸溶解,高氨酸冒烟驱除氟后,采用氢氧化钠一氯化钠体系沉淀Fe(Ⅲ),过滤后加入过量EDTA,在pH 5.5条件下,用硫酸铜标准溶液滴定过量的EDTA,获得了令人满意的结果.1 主要试剂与仪器吡啶基偶氮萘酚(PAN)乙醇溶液:2g·L~(-1)乙酸-乙酸钠缓冲溶液:PH 5.5混合液:50g·L~(-1)氯化钠与10g·L~(-1)氢氧化钠溶液按1:1混合.对硝基酚乙醇溶液:2g·L~(-1)EDTA标准溶液:0.02mol·L~(-1),称取基准乙     

碱稳定样品法测定降水中3种有机酸

建立了氢氧化钠稳定样品的离子色谱梯度淋洗测定大气降水中3种有机酸(乙酸、甲酸、草酸)的分析方法。用淋洗液在线发生器(RFC-30)产生梯度氢氧化钾溶液,以及Ion Pac AS19分离柱、IonPacAG19保护柱,确定了最佳梯度淋洗程序,可在36 min内同时测定大气降水中有机酸(乙酸、甲酸、草酸)和无机阴离子。并探讨了乙酸、甲酸、草酸标准溶液的稳定性,在有机酸标准溶液调为碱性(pH≥10)条件下,且于4℃下冷藏密封保存,乙酸、甲酸、草酸在10天内具有较好的稳定性。如空白试验中有微量甲酸、氯离子,实际样品和标准溶液测定时需相应扣减。乙酸、甲酸和草酸线性回归方程相关系数均大于0.999 5,方法检出限分别为0.002、0.003、0.002 mg/L,实际降水样品测定时乙酸、甲酸、草酸的相对标准偏差在0.3%～3.3%,加标回收率在93.0%～105.0%。本方法检出限低、精密度、准确度好,操作简便、灵敏、实用,可应用于实际大气降水分析,为相应标准方法(HJ1004-2018)提供了参考。     

EDTA滴定法快速测定铝锰镁合金中铝和镁方法探讨

以HCl溶解HClO4冒烟使试样完全溶解后,利用铝是两性元素的特性,加入过量的NaOH使Mg、Fe、Mn生成氢氧化物沉淀,过滤与铝分离.将滤液定容,移取部分在过量EDTA存在下,用HCl调节pH 4左右,加热煮沸使铝与EDTA配位络合,以PAN为指示剂,用CuSO4标准溶液返滴定过量的EDTA,加氟化钠取代出与铝定量配位络合的EDTA,再用CuSo4标准溶液滴定取代出的EDTA,求得铝量.将过滤出的Mg、Fe、Mn等氢氧化物沉淀,用热的稀HCl及H2O2溶解后,用NH3·H20(1+1)调节pH 5～6,加入铜试剂使Fe、Mn沉淀与Mg分离,于滤液中加NH4Cl缓冲液,以铬黑T为指示剂,用EDA标准溶液滴定镁量.     

EDTA容量法快速测定酸法生产金属镓的液体物料中镓含量

建立了在酸法生产金属镓过程中,用NH4F掩蔽溶液中的铝,加入过量的EDTA标准溶液使之与镓元素完全络合,调整条件试剂硼酸溶液和无水乙醇的加入量,保证终点的准确判断,过量EDTA以PAN为指示剂用硫酸铜标准溶液回滴求得液体物料中镓含量的分析方法.实验表明,方法的相对标准偏差(RSD)为2.8％～6.5％,加标回收率为97.14％～104.0％.方法有较高的准确性和可靠性,且测定结果精密度高,可实现酸法生产金属镓液体物料中镓含量的快速检测.     

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.     

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。     

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.

     

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.     

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.     

解决能源问题的新途径——光解水制氢的研究

面对日益枯竭的能源危机,氢能是一种洁净、最有前景的替代能源。目前在各种制氢的方法中光催化分解水制氢的研究最多,光解水过程中催化剂最关键,本文对利用太阳能光解水的途径、提高光催化反应效率以及光催化剂的开发研究进行了综述。