硫酸亚铁铵滴定法连续测定钢铁中铬钒

提出了一种硫酸亚铁铵滴定法连续、快速测定钢铁中铬钒的方法。硫酸-磷酸混合酸溶解样品,硝酸分解碳化物,直接用少量硝酸银、过硫酸铵催化氧化溶液中低氧化数锰、铬、钒,稀盐酸还原中、高氧化数锰,以苯代邻氨基苯甲酸为指示剂,硫酸亚铁铵滴定铬(Ⅵ)、钒(Ⅴ)合量。不分解指示剂,直接用高锰酸钾与亚砷酸钠反应产生的中等氧化数锰,选择性氧化钒(Ⅳ),在尿素存在下,亚硝酸钠还原过量氧化剂,硫酸亚铁铵滴定钒(Ⅴ)。测钒时,指示剂无校正值;45 mg以下钨不干扰铬钒的测定;并扩展测钒方法的应用,讨论废液处理。方法简便、准确、快速、实用、兼容性好。     

关于钒的滴定法中铬、铈的干扰问题

滴定法测定钒常采用在室温条件下,用高锰酸钾溶液氧化至高价后,用硫酸亚铁铵标准溶液滴定,指示剂则多数采用邻苯氨基苯甲酸。在此方法中主要的干扰元素为铬和铈。铬是钢铁中常用的合金元素,在冷溶液中用高锰酸钾溶液氧化钒时可能有少量铬(Ⅲ)被氧化至高价,可加亚砷酸钠溶液使铬(Ⅵ)选择性地被还原,从而避免其干扰。氧化还原测定也是测定铈的主要方法之一。四价铈是强氧化剂,Ce~(4+)/Ce~(3+)电对的氧化还原电位与溶液介质和酸的浓度有关,在1mol·L~(-1)的HCl、HNO_3、HClO_4和0.5mol·L~(-1)H_2SO_4溶液介质中分别为1.28V、1.61V、1.70V和1.44V。而且在磷酸介质中由于生成铈与磷酸根的络合物,使其氧化还原电位降低,因此三价铈更容易被氧化。在磷酸介质中用硝酸铵或高锰酸钾可使铈定量氧化。因此,在钒的滴定法测定中,如果有铈     

亚铁容量法测铈中几个问题的探讨

亚铁容量法测定矿石中铈是常用方法,鉴于该法存在分析结果易产生系统偏差,还原锰需使用毒性试剂亚砷酸钠,不适于含钒试样的测定等问题。本文采用一元线性回归法求亚铁标准溶液的滴定度和修正因数;以亚硝酸钠消除锰的干扰;用酒石酸钾钠分离钒,克服了原方法的缺点。主要试剂亚铁灵指示剂-1.5克1.10-邻菲罗啉溶于100毫升1.0％硫酸亚铁铵溶液中;0.2％邻苯氨基苯甲酸指示剂;铈标准溶液-取0.6142克光谱纯二氧化铈预先在850℃灼烧半小时,按不含钒试样分解,用1.5％(V/V)硫酸稀至500毫升,此溶液1毫升含1毫克铈;0.007N硫酸亚铁铵标准溶液[内含4％(V/V)硫酸]。亚铁标准溶液的标定于6个250毫升锥形瓶中分     

高速钢中锰、铬、钒的连续容量法测定

高速钢中锰含量较低,而铬量较高,同时含有大量的钨,要想用连续容量法进行锰铬钒的测定是有一定困难的。我们采用硫磷混酸溶样后,以高氯酸加热冒烟氧化,锰铬钒分别被氧化为三、六、五价,以二苯胺磺酸钠为指示剂,用亚铁溶液滴定锰铬钒总量。然后补加磷酸,加热冒烟并驱尽高氯酸,此时大部分铬又成三价状态,而只是锰钒被氧化,继加亚砷酸钠还原部分高价铬,再以亚铁溶液滴定锰钒合量。最后于室温下用高锰酸钾氧化钒,测得钒量,并用差减法求得     

读者园地

三价锰滴定法主要的干扰元素是钒和铈。在氧化过程中,钒(Ⅳ)及铈(Ⅲ)也同时被氧化至高价,而在最后滴定时也定量参与反应。故应从测得的结果中扣除钒(铈)的量。如果已知试样中钒(铈)的含量,或者已用其它方法测得钒(铈)的含量,则可按1.00％钒相当于1.08％锰,和0.10％铈相当于0.04％锰的比例进行校正。如果试样是否含钒(铈)是未知的,则可按常规的方法测定钒(铈)后进行校正。也可以用改变滴定方式来消除钒(铈)的干扰。即在滴定时定量地加入过量的硫酸亚铁铵滴定溶液,然后用标准高锰酸钾溶液回滴过量的铁(Ⅱ)。在此过程中。钒(Ⅴ)先被铁(Ⅱ)还原,后又被回滴定的标     

亚砷酸还原高锰酸：锰的氧化数

在硫酸介质中,以亚砷酸还原高锰酸,探索锰的氧化数.1.亚铁溶液滴定高锰酸钾溶液.2.亚砷酸钠溶液滴定高锰酸钾溶液,再以亚铁溶液滴定.3.亚砷酸钠溶液滴定高锰酸钾溶液后,补加亚砷酸钠溶液,使其加入总量为还原高锰酸钾Mn(Ⅶ)→Mn(Ⅲ)的理论值,再以亚铁溶液滴定.通过亚铁溶液消耗量,计算锰的氧化数.本文证明:亚砷酸还原高锰酸后,锰的氧化数为 3.0,而不是70年以来,文献[1～3]一直认为的亚砷酸还原高锰酸,锰的平均氧化数 3.3.     

电感耦合等离子体原子发射光谱法测定偏钒酸钠中钒含量

偏钒酸钠主要用作化学试剂、催化剂、催干剂、媒染剂等,例如陶瓷工业用作釉料,化工领域用于制取五氧化二钒,钒含量是评判偏钒酸钠产品质量的关键指标。通常采用过硫酸铵或高锰酸钾氧化-硫酸亚铁铵滴定、电位滴定等传统化学分析方法测定钒铁、钒氮合金、金属钒等样品中高含量钒[1],其缺点是操作繁杂、劳动强度大、检验周期长达2~3h,难以满足现代工业快节奏生产对产品质量控制的要求。电感耦合等离子体原子发射光谱法(ICP-AES)     

可视滴定法测定铝钒中间合金中的钒时称样量和滴定液浓度的优化

用可视滴定法测定铝钒中间合金中的钒时,对称样量和硫酸亚铁铵滴定液浓度的关系进行了探讨。实验发现,基体铝对于铝钒合金中钒的测定无影响。常见的铝钒合金范围为50%～60%,低于50%和高于标准上限0.5%钒含量的合金没有实验样品,通过向样品溶液中加入钒标准溶液可模拟铝钒合金试样。依据化学分析等物质量反应定律,选择不同钒含量的试验样品,对钒的称样量和滴定液浓度进行优化,确定了硫酸亚铁铵滴定液的浓度与滴定液消耗体积的合适关系。     

铝锰合金中锰的快速测定——三价锰容量法

铝锰中间合金中的锰高达10%,宜采用容量法测定。本法用磷酸溶样,并在一定温度下以硝酸铵将锰(Ⅱ)氧化成三价状态的磷酸锰,再用亚铁标准溶液滴定,将锰(Ⅲ)定量还原成锰(Ⅱ),从消耗亚铁标准溶液量求得锰量。方法操作简便快速、滴定终点明显、干扰元素少、试剂用量少,单样分析仅需10分钟,已用于生产控制分析,实践证明是测定铝锰合金中锰的好方法。试剂配制硫酸亚铁铵标准溶液(0.025N);苯代邻氨基苯甲酸溶液(0.2%):0.2克指示剂溶于100毫升0.2%热碳酸钠溶液中。     

锋钢中铬钒的连续测定

锋钢(钨钼铬钒系列)中铬钒的分析,都基于氧化还原的理论,在化验室的日常工作中,特别是炉前快速分析铬钒,都是由两人分别称样,将铬钒氧化成六价和五价,再用不同浓度的硫酸亚铁铵标准溶液,将其还原为三价和四价,然后,根据其所消耗的标准溶液的体积,以标准样品控制,计算其含量.由于该两元素反应的原理相同,所用的试剂基本一致,因此,将分开测定的两种元素,合并为称一个样品,得出两个结果,通过大量的试验,连续测定的结果,与单独测定的结果,其误差均在允许范围内、这样、不仅可以节约分析人员一个.而且还可以节约大量的药品,分析时间亦可由本化验室的15min缩短到7～8min.1 试剂硫磷混合酸:H_2SO_4+H_3PO_4+H_2O=2+2+6高锰酸钾溶液:20g·L~(-1)亚硝酸钠溶液:2g·L~(-1)亚砷酸钠溶液:1g·L~(-1)铬钒指示剂:2g·L~(-1),用2g·L~(-1)的碳酸钠溶     

Furyl- and thienyl-silatranes and germatranes

We review our research on the synthesis and study of the physical and biological properties of furyl- and thienylgermatranes and -silatranes.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 725–732, June, 1992.     

Review and patents and literature

The use of the insect cell/baculovirus expression system for producing recombinant proteins of bacterial, plant, insect, and mammalian origin has become widespread. The popularity of this eukaryotic expression system is due to many factors, including (1) potentially high protein expression levels, (2) ease and speed of genetic engineering, (3) ability to accommodate large DNA inserts, (4) protein processing similar to higher eukaryotic cells (e.g., mammalian cells), and (5) ease of insect cell growth (e.g., suspension growth). The following review of the literature discusses two engineering aspects of recombinant protein synthesis by insect cell cultures: bioreactor scale-up and insect cell line selection. Following this review patent abstracts and additional literature pertaining to expression of recombinant proteins in insect cell culture are listed.     

Ground- and excited-state aromaticity and antiaromaticity in benzene and cyclobutadiene

The aromaticity and antiaromaticity of the ground state (S 0), lowest triplet state (T 1), and first singlet excited state (S 1) of benzene, and the ground states (S 0), lowest triplet states (T 1), and the first and second singlet excited states (S 1 and S 2) of square and rectangular cyclobutadiene are assessed using various magnetic criteria including nucleus-independent chemical shifts (NICS), proton shieldings, and magnetic susceptibilities calculated using complete-active-space self-consistent field (CASSCF) wave functions constructed from gauge-including atomic orbitals (GIAOs). These magnetic criteria strongly suggest that, in contrast to the well-known aromaticity of the S 0 state of benzene, the T 1 and S 1 states of this molecule are antiaromatic. In square cyclobutadiene, which is shown to be considerably more antiaromatic than rectangular cyclobutadiene, the magnetic properties of the T 1 and S 1 states allow these to be classified as aromatic. According to the computed magnetic criteria, the T 1 state of rectangular cyclobutadiene is still aromatic, but the S 1 state is antiaromatic, just as the S 2 state of square cyclobutadiene; the S 2 state of rectangular cyclobutadiene is nonaromatic. The results demonstrate that the well-known "triplet aromaticity" of cyclic conjugated hydrocarbons represents a particular case of a broader concept of excited-state aromaticity and antiaromaticity. It is shown that while electronic excitation may lead to increased nuclear shieldings in certain low-lying electronic states, in general its main effect can be expected to be nuclear deshielding, which can be substantial for heavier nuclei.     

多环芳二酐型聚酯亚胺膜的透气性能

多环芳二酐型聚酯亚胺膜的透气性能李悦生，丁孟贤，徐纪平（浙江大学高分子科学与工程研究所，杭州，３１００２７）（中国科学院长春应用化学研究所）关键词聚醚酰亚胺，聚酯酰亚胺，膜，透气性通常的聚酰亚胺加工性能较差，在芳环二酐的苯环间引入醚键等柔性基团后，其...     

Determination and study on residue and dissipation of benazolin-ethyl and quizalofop-p-ethyl in rape and soil

A QuEChERS (quick, easy, cheap, effective, rugged, and safe) method for the determination of benazolin-ethyl and quizalofop-p-ethyl in rape and soil by high-performance liquid chromatography-tandem mass spectrometry has been developed in this study. The residue and dissipation of benazolin-ethyl and quizalofop-p-ethyl in rape and soil were determined with the developed method. The half-lives of benazolin-ethyl in rape straw and soil were 3.7–5.1 days and 14.3–26.3 days, respectively. The half-lives of quizalofop-p-ethyl in rape straw and soil were 5.0-6.1 days and 0.3–9.7 days, respectively. The residue of benazolin-ethyl and quizalofop-p-ethyl in rapeseed and soil were below the detection limit (i.e., 0.5?mg?kg^?1, the maximum residue level of European Union for quizalofop-p-ethyl).