甲基紫分光光度法测定食盐中的添加剂碘酸钾

研究了碘酸钾、碘化钾与甲基紫在盐酸介质中的显色反应 ,反应产物之最大吸收波长λmax为 650nm ,并由此建立了一个简单、快速、实用的分光光度测定食盐中微量碘酸钾的新方法。在最佳实验条件下 ,碘酸钾质量浓度在 0～ 1 60 μg/ 2 5mL内服从比耳定律 ,其线性相关系数r为 0 .9996。本法用于加碘食盐中微量碘酸钾的测定 ,结果与紫外光度法所得结果基本一致     

读者园地

问 :1 .燃烧 -碘量法测定钢铁中硫 ,可用碘标准溶液或用碘酸钾标准溶液滴定 ,两者有何不同 ?2 .燃烧 -碘量法测定钢铁中硫时 ,对淀粉吸收液有何要求 ?——读者　　李纬　　　　答 1 :用燃烧 -碘量法测定硫 ,将试样在氧气中燃烧生成的 SO2 导入吸收液中生成 H2 SO3 ,以淀粉为指示剂 ,用碘或碘酸钾标准溶液进行滴定 ,根据所消耗的标准溶液量计算出试样中硫含量 ,两者原理是相同的。用碘标准溶液滴定 ,试剂配制方便 ,适用于测定含硫量 w( S)≥ 0 .0 1 %的试样。对含硫量 w( S)≤ 0 .0 1 %的试样最好用碘酸钾 -碘化钾标准溶液滴定 ,因为它比…     

离子色谱法测定婴幼儿营养米粉中的碘含量

采用离子色谱分离和脉冲安培检测婴幼儿营养米粉中添加的碘化钾或碘酸钾含量.考察了蛋白质去除的方法和试剂用量,优化了超声提取净化方案,研究了碘酸钾转化成碘化钾的最佳还原剂用量,进行了淋洗液浓度和检测器波形等仪器条件的选择.在优化实验条件下,碘化钾和碘酸钾的线性范围均为1～100 μg/L,相关系数分别为0.999 1和0....     

邻联甲苯胺显色光度法测定微量碘的研究

研究了在盐酸介质中,利用碘酸钾氧化性使邻联甲苯胺显色,建立了光度法测定碘的方法。在选定的条件下,有色溶液的最大吸收波长为426nm,碘的含量在0~20μg/25mL范围内符合比耳定律,表观摩尔吸光系数为1.13×105L.mol-1.cm-1。方法简单、快速、准确、选择性好、灵敏度高,用于测定加碘食盐中的碘,结果满意。     

碘量测测定低硫

硫是钢中有害元素 ,随着工厂的发展和对材料质量要求的提高 ,需对低硫进行精确测定。本法用HV- 1 1高速自动定碳定硫仪进行了一系列的分析试验。试验证明 ,可以满足钢中低硫 (特别是 ws<0 .0 1 % )测定精度的要求 ,克服了正常分析范围内该仪器对低硫测定精度的要求的不足 ,做到了碳、硫同时测定。1　试验部分1 .1　仪器与试剂HV- 1 1高速自动定碳定硫仪管式炉 ,电阻炉变压器碘酸钾标准溶液 :称取碘酸钾 0 .1 78g,溶于水后稀释至 1 L,浓度为 0 .0 0 5mol· L-1。分取此液50 ml,稀释至 1 L,加碘化钾 1 g,摇匀 ,配成0 .0 0 0 2 5mol·L-1碘…     

动力学荧光法分析痕量碘的研究

基于在磷酸介质中，碘能催化过碘酸钾氧化罗丹明6G的反应，使荧光猝灭，建立了催化荧光法测定痕量碘的新方法。方法的检出限为0．019mg/L，线性范围为0．020mg/L-0.80mg/L，可直接用于加碘食盐、海带、紫菜和盐酸胺碘酮药片中碘的测定。     

催化动力学光度法测定茶叶和中药中的单宁

在盐酸介质中,微量单宁对碘酸钾氧化丙基红的褪色反应有显著的催化作用,据此建立了催化动力学光度法测定微量单宁的新方法。方法的线性范围为0．1～3．0／μg／mL,检出限为0．04／μg／mL。本法简便、快速、灵敏度高和选择性较好,用于茶叶和中药五倍子、诃子中单宁含量的测定,结果满意。     

介绍一种测定合金中低硫的简易电导法

燃烧-碘酸钾滴定法是目前测定大多数合金中硫的最普遍采用的方法。此法简单迅速,但准确度较差,不适宜做低硫的测定。现行测定合金中低含量硫(0.00x％)较准确和灵敏的方法有燃烧-碘酸钾滴定法、比色法及重量法。除前者可用于日常分析之外,后两者准确度虽高但手续都较烦琐,不易掌握,易受条件限制。电导法定硫,虽有报导,但研究     

催化光度法测定痕量对苯二酚

在硫酸介质中，以草酸为活化剂，痕量对苯二酚对碘酸钾氧化天青Ⅱ的褪色反应具有明显的催化作用，据此建立了催化光度法测定痕量对苯二酚的新方法。方法的线性范围是0．04～1．20mg／L，检出限为0．008mg／L。方法操作简便，灵敏度高，选择性好，用于自来水、实验室废水和显影液中对苯二酚的测定，结果满意。     

微分脉冲极谱法测定水中痕量的Se(Ⅳ)和Se(Ⅵ)

本文使用悬汞电极微分脉冲极谱法于硒(Ⅳ)-亚硫酸钠-高氯酸-氨水-酒石酸铵-碘酸钾体系的极谱催化波测定水中痕量的硒(Ⅳ)和硒(Ⅵ).选择了最佳测定条件,试验了Te~(4+)、Hg~(2+)、腐植酸等十三种物质的影响程度,检出限0.01μg/1。硒浓度在0～1.0μg/1的范围内与峰电流成线性关系,相对标准偏差10-14％,回收率为95-100％。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.