钒钼黄分光光度法测定有机化合物中的微量磷

介绍了钒钼黄分光光度法测定有机化合物中微量磷的方法。有机磷经浓硫酸-硝酸氧化分解,转化为正磷酸。在一定酸度下,溶液中的磷与偏钒酸盐和钼酸盐作用,形成稳定的黄色三元杂多酸钒钼磷酸,再用分光光度法测定磷含量。     

铅的生物富集效应

铅以微量元素的含量水平，广泛分布于动、植物的人体中。对比大量的动植物种群及各种年龄组的人群，似乎铅在一定的分子组态，特别是生物有机铅，不一定都是有害物质。相反可起一定的新陈代谢调节作用。或者可称为新陈代谢调节剂。特别是在动物、植物、人体中铅为微量、超微量状态时，铅更显现调节作用。     

Dawson型钒代磷钼酸在酮/醇缩合中的催化性能

合成了Dawson型磷钼酸和钒取代磷钼酸, 用UV-Vis、 IR和XRD表征了结构, 用pH计考察了在不同介质中的酸性. 以苯乙酮和醇的缩合反应作为探针反应, 考察了磷钼酸中钒含量、磷钼酸用量及醇用量等因素对磷钼酸催化性能的影响. 结果表明, 钒取代钼后使Dawson型磷钼酸在有机介质中的酸性减弱. 当H_6P_2Mo_(18)O_(62)∶苯乙酮∶乙二醇的物质的量比为6∶1000∶2000, 回流反应6 h时, 缩酮收率为89.2 %. 在合成缩酮的反应中, 磷钼酸的"假液相"性使其催化活性明显增强, 但随着钒取代数增加, 钒取代磷钼酸的催化性能减弱;醇分子的空间位阻增大, 磷钼酸的催化活性也降低.     

添加稀土的钒钼磷杂多化合物的制备和表征

制备了不同稀土掺杂的钒钼磷杂多酸催化剂,采用XRD、TG、IR、TPR等手段表征了杂多酸催化剂体系上添加不同稀土的作用.结果表明,稀土的掺杂对钒钼磷的晶相形成有利,促进了催化剂表面V物种、Mo物种的还原.     

磷钼钒杂多酸光度法测定钒

磷钼钒杂多酸早已用于磷的光度分析,其它应用尚未见报道。本文提出利用磷钼钒杂多酸光度测定高速钢中常量的钒,共存元素中铬、钴的影响以试样空白扣除,钨的负干扰可采用经验系数补正,样中1％Si和1％Nb不干扰测定。方法简便、快速、准确。本文还提出了在一定条件下形成磷钼钒酸、磷钨钒酸和磷钨钼酸的经验规律。 1 试剂与仪器 钼酸铵溶液:53g·L~(-1) 盐磷混酸:1.19g·ml~(-1)盐酸+1.74g·ml~(-1)磷酸=3+2 钒标准溶液:0.900mg·ml~(-1)(里偏钒酸铵配制并以滴定法标定) 721型分光光度计 2 分析方法称取试样0.1000g于200ml锥形瓶中(同时称一份不含钒的钢样作试剂空白A_0),加盐磷混酸1.5ml,硫酸(1+1)8ml,加热溶解,滴加浓硝酸助溶,继续加热     

干法灰化-碱熔-离子选择性电极法测定植物样品中氟

<正>氟是生物体内重要的微量元素之一,也是环境化学和生命科学研究中的常见元素。在生态地球化学中,氟为必测定元素,含量很低,但具有高度的生物活性,在动植物体内无生物降解作用~([1-2])。氟化物污染空气后,能够在植物中富集,对植物的生长和发育造成严重的危害,即使低水平的污染也能通过生物富集和食物链作用对人体造成一定的危害,不利于身体健康~([3])。同时人体缺氟或氟过量也会对健康造成不良的影响~([4])。因此,分析植物样品中氟含量的变化对研究生态地球化学以及人体和动植物的健康特征具有重要的意义。     

石煤中钒的化学物相分析

将石煤中的钒物相分为氧化铁矿物和黏土矿物中的钒、云母类矿物中的钒、电气石和石榴子石中的钒等3相。分别采用盐酸(1+3)溶液浸取氧化铁矿物和黏土矿物中的钒,氢氟酸(1+3)溶液浸取云母类矿物中钒,过氧化钠碱融分解电气石和石榴子石中钒。采用电感耦合等离子体原子发射光谱法测定钒总量和各相浸取液中的钒,同时采用磷钨钒酸分光光度法对钒总量和第一、第二相中的钒进行测定。两种方法的测定结果相符,且钒各物相分量的加总和总量的相对偏差允许限均远远小于20%,满足《地质矿产实验室测试质量管理规范》(DZ/T 0130-2006)的规定。     

贵州三穗县钒矿石及矿渣微量元素综合利用评价

目的：探讨钒矿及矿渣中的微量元素含量,以便为钒矿石和矿渣的有效利用提供重要参考。方法采用ICP-MS对钒矿石中的微量元素进行分析,并对钒矿石和矿渣中的微量元素利用进行了评价。结果钒矿中的钒利用率仅为64.9％,矿渣中的V、 Cr、 Zn、 Mo、 Cd和U的含量很高。结论分析认为, V、 Cr、 Zn、 Mo、 Cd和U可能会对环境造成一定的影响。     

锌从土壤向食物链的迁移

锌是生物必需微量元素，但过多时对动植物都有毒害。本文对锌在人类食物链中的行为及在土壤－－植物－－人类和动物系统中的迁移，决定农业系统中锌动力学的关键过程，锌在作物可食部位的丰度，影响锌生物有效性的土壤环境，植物因子及锌在食物中的需要量等作了综述了论述。     

锗的环境生态研究

锗是分散性元素，在动、植物中属于微量，超微量元素。在动物中，锗多存在于肝脏、肌肉，亦见于骨骼及鱼鳃中，在植物中，锗主要分布于叶子及糖类淀粉贮藏的器官中。通过动植物肿瘤的分析，说明锗不是致病元素。锗用于保健，主要在于促进糖类代谢，提高免疫力，而不是直接杀死癌细胞或其它病原体。     

Synthesis of γγγ-trifluorocarbonyl compounds

γγγ-Trifluorocarbonyl compounds are easily obtained in a good yield by introduction of the 1,1,1-trifluoroethyl moiety (CF₃-CH₂-) on the -methylene group of a ketone.     

Die Kristallstruktur des W3CoB3 und der dazu isotypen Phasen Mo3CoB3, Mo3NiB3 und W3NiB3

Zusammenfassung Mo₃CoB₃, Mo₃NiB₃, W₃CoB₃ und W₃NiB₃ kristallisieren in einem eigenen Typ (W₃CoB₃-Struktur). Das trigonal prismatische Bauelement [T ₆B]^* ist zu Ketten vereinigt, wobei B₃-Gruppen entstehen. Die Phasen sind vermutlich Bor-reicher als obiger Formel entspricht.

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The crystal structure of W₃CoB₃ and the isotypic phases Mo₃CoB₃, Mo₃NiB₃, and W₃NiB₃

Mo₃CoB₃, Mo₃NiB₃, W₃CoB₃, and W₃NiB₃ were found to possess a new type of crystal structure (W₃CoB₃-structure type). Trigonal prismatic groups [T ₆B]^* are linked together forming chains in such a way that B₃-groups occur. These borides do probably exist with a larger amount of boron as to compared with the formula.

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K3SbSe3, Rb3SbSe3 und Cs3SbSe3 – Synthese und Kristallstruktur

K₃SbSe₃, Rb₃SbSe₃, and Cs₃SbSe₃ – Synthesis and Crystal Structure The compounds K₃SbSe₃, Rb₃SbSe₃ and Cs₃SbSe₃ were synthesized by heating mixtures of Sb₂O₃ and an alkalicarbonate in a stream of hydrogen saturated by selenium in a temperature range between 750 °C and 800 °C. The compounds crystallize isostructural with Na₃AsS₃. A comparison of atomic distances and bond angles with those of the isostructural arsenic and bismuth compounds shows the effect of lone pairs.     

γ-Nitro-γ-butyrolacton

γ-Nitro-γ-butyrolactone By oxidation of 3-(1-nitro-2-oxocyclohexyl)propanal ( 1 ) with KMnO₄, besides 3-(1′-nitro-2′-oxocyclohexyl)pripionic acid ( 2 ), the complete hydrolysis product 4-oxononanedioic acid ( 4 ) and the oxidized semi-hydrolysis product 5-(2-nitro-5-oxotetrahydro-2-furyl)pentanoic acid ( 3 ) were formed. The crystalline 3 decomposes at r.t. forming 4 and nitrous gases; its structure was established by X-ray determination.     

Freezing the polarization of CH3NH3PbI3 and CH3NH3PbI3-xClx perovskite films

Thin films of methylammonium lead halides, CH₃NH₃PbI₃ and CH₃NH₃PbI_3-xCl_x, were deposited onto symmetrical microstructured electrode arrays of gold or platinum on Si/SiO₂ wafers. Polarization studies were carried out on perovskite films under vacuum in the dark. For poling, a constant voltage was applied to the samples while the temperature was cycled between 295 K and 4 K. The measured current densities depending on the temperature showed distinct characteristics relating strongly to the crystal phase and the dielectric properties of the perovskite films. Voltage sweeps were carried out at different scan rates at specific temperature intervals after poling. The polarization of the films due to the migration of iodide vacancies in direction of the blocking perovskite/metal interface was frozen almost up to room temperature. Charge carriers were only able to cross the blocking barrier and contribute to the current where the ions have accumulated during poling. All J-V curves showed hysteresis: inverted and regular hysteresis at room temperature and below, respectively. Inverted hysteresis originates from the slow accumulation of ions at the blocking barrier, while regular hysteresis arises from a distortion in the adjacent crystals which will be discussed.     

K3BiSe3, Rb3BiSe3 und Cs3BiSe3 – Substitutionsvarianten des Th3P4-Typs

K₃BiSe₃, Rb₃BiSe₃, and Cs₃BiSe₃ – Derivatives of the Th₃P₄ Structure Type The compounds K₃BiSe₃, Rb₃BiSe₃, and Cs₃BiSe₃ were synthesized by heating mixtures of Bi₂O₃ and the respective alkalicarbonate in a stream of hydrogen saturated by selenium at 850°C. Thin crystals of the compounds appear red in transmitted light. They crystallize isostructural with Na₃AsS₃, space group P2₁3, lattice constants a = 9.771(5) Å, a = 10.161(3) Å, and a = 10.587(5) Å for K₃BiSe₃, Rb₃BiSe₃, and Cs₃BiSe₃, respectively. The Na₃AsS₃ structure type is a derivative of the Th₃P₄ structure type.     

Synthesis of some derivatives of 3-amino-3-desoxyerythrose and 3-amino-3-desoxy-D-3-erythrose

The synthesis of derivatives of 3-amino-3-deoxy-L-erythrose by LAH or LAD reduction of the oxime of 1,2-O-isopropylidene α-L -glycero-tetros-3-ulofuranose is described.     

Die Akzeptoreigenschaften von AsCl3, AsBr3, asJ3, SbCl3, SbBr3 und SbJ3

Zusammenfassung Es wurden die Enthalpien der Reaktionen von AsCl₃, AsBr₃, AsJ₃, SbCl₃, SbBr₃ und SbJ₃ mit Tributylphosphat, N,N-Dimethylacetamid und Hexamethylphosphorsäuretriamid bestimmt. Das Verhalten der Addukte bei Gegenwart eines Überschusses der Donoren wird beschrieben.

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Acceptor properties of AsCl₃, AsBr₃, AsI₃, SbCl₃, SbBr₃, and SbI₃

The enthalpies of the reactions of AsCl₃, AsBr₃, AsI₃, SbCl₃, SbBr₃ and SbI₃ with tributylphosphate, N,N-dimethylacetamide and hexamethylphosphoric acid triamide were measured. The behavior of the adducts in the presence of excess donor molecules is described.

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3x-pyrrolizin-3-ones

Condensation of pyrrole-2-dithiocarboxylates with CH acids containing ester groups, in the KOH-DMSO system, was used to prepare previously unknown 1-alkylthio-3H pyrrolizin-3-ones. The latter, treated with secondary amines, are readily converted to the corresponding 1-amino derivatives.     

3-H-pyrrolizin-3-ones

Previously unknown 1-alkylthio-3H-pyrrolizin-3-ones have been obtained by the condensation of pyrrole-2-dithiocarboxylates with CH acids containing ester groupings in the KOH-DMSO system. On treating the products with secondary amines they are readily converted into the corresponding 1-amino derivatives.Irkutsk Branch of the Russian Academy of Sciences, Irkutsk 664033. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 919–924, July, 1996. Original article submitted May 2, 1996.