Enhancement of Demasking of Fluoride Ion From its Aluminum Complexes by Dilution in the Determination With a Fluoride Ion-Selective Electrode

Abstract

In the determination of fluoride ion with an ion-selective electrode the permissible concentration of aluminum increases markedly with decreasing the fluoride concentration in 0.5M citrate buffer solutions at pi I 6. As the accuracy is constant over a concentration range down to 10^?5 M F^? where a Nernstian relation holds fluoride determinations can be accomplished by the successive dilution method. The dilution steps are repeated until the last two results are in agreement, while the concentration of citrate is kept constant. As the ionic strength is kept constant with citrate, the addition of sodium chloride to the buffer is not necessary. Several samples, especially glasses, have been analyzed successfully.     

Spectrophotometric Determination of Copper(II) as the Azide Complexes,in the Presence of Iron(III) Cations

Abstract

A method for the spectrophotometrio determination of copper(II), in the presence of iron(III) cations (excess), was stablished. The masking of iron is made with sodium fluoride salt in 50 % (v/v) water/acetone medium. In the recommended conditions, absorbances for cupric complexes are measured at 435 nm where molar absorptivity is 6.00 × 10³ 1 mol^?1 cm^?1.

The stable ayetern obeys Beer's law and is suitable for the copper determination in concentration range from 2.0 to 9.0 mg 1^?l. The iron(III) ion interference (until ca. 600 mg 1^?l) can be completely suppressed. The influence of diverse ions and several others factore were studied.

The results show that copper(II) can be accurately determined by azide apectrophotometric method, if the samples were suitablely treated by the recommended procedure.     

SPECTROPHOTOMETRIC DETERMINATION OF TRACE AMOUNTS OF FLUORIDE IN PLUTONIUM

Abstract

A simple and rapid spectrophotometric method for the determination of 10 to 70 μg of fluoride with Eriochrome Cyanine R in up to 10 mg of plutonium has been developed. In this method interference from the plutonium is eliminated by reduction of this element to the tripositive oxidation state with mercaptoacetic acid.     

Crystallization and reinforcement of poly (vinylidene fluoride) nanocomposites: Role of high molecular weight resin and carbon nanotubes

The effect of high molecular weight resin and multi-walled carbon nanotubes (MWCNTs) on the crystallization, rheological and dynamic mechanical properties of poly (vinylidene fluoride) (PVDF) composites was investigated. A synergetic effect of the high molecular weight resin and MWCNTs on the nucleation in the crystallization process of the matrix has been observed, and their contributions to the crystallization of the matrix are two-sided. The composites containing both the high molecular weight resin and MWCNTs have much higher crystallization peak temperatures but lower crystallinity, especially for samples with high MWCNT content. For the isothermal crystallization at relative high temperatures, higher Avrami exponent and shorter half-time of crystallization are observed for the composites containing both the high molecular weight resin and MWCNTs. The introduction of the high molecular weight resin not only reinforces the matrix, but also promotes the dispersion of MWCNTs. The reinforcement and synergetic nucleation effects of the high molecular weight resin and MWCNTs were also confirmed by dynamic mechanical analysis.     

Microwave-assisted Claisen rearrangement of naphthyl 2-propynyl ethers: synthesis of naphthofurans

An efficient two-step approach for the synthesis of naphtho[1,2-b]furans and naphtho[2,1-b]furans has been developed. Various functionalized propargyl alcohols were etherified with α- or β-naphthol under Mitsunobu reaction conditions to give naphthyl 2-propynyl ethers, which underwent a facile microwave-assisted Claisen rearrangement and concomitant anionic cyclization to yield naphthofuran derivatives under basic reaction conditions.     

Optical Properties of the Orchid Colored Silver(II) Fluoride Cs2AgF4

Orchid colored powder samples of Cs₂AgF₄ were prepared by a solid state reaction from CsF and AgF₂. The diffuse reflectance spectrum of a powder sample of Cs₂AgF₄ was measured in the UV/Vis region. It shows three broad bands, two in the visible‐light region at 650 nm, 500 nm and one in the UV region at 259 nm. The bands are assigned to F 2p → Ag 4d and Ag 4d → Ag 4d transitions. The optical band gap for Cs₂AgF₄ determined from the UV/Vis diffuse reflectance spectrum is approx. 2.17 eV. In order to interpret the observed absorptions, the theoretical absorption spectrum of Cs₂AgF₄ was obtained from density functional calculations.     

How does γ-irradiation affect the properties of a microfiltration membrane constituted of two polymers with different radiolytic behavior?

The objective of this work is to present the behavior of a fluorinated microporous membrane composed of poly(vinylidene fluoride) (PVDF) mechanically reinforced by a polyamide-66 (PA-66) fabric under γ-irradiation with dose ranging between 0 and 100 kGy, in inert atmosphere and at room temperature. Particular attention was paid to the evolution of mechanical properties, the surface morphology and pores size distribution of this membrane, in order to study the filtration capacity and selectivity with increasing radiation dose. Moreover, the repartition of the generated radicals onto the two components of the membrane was achieved by electron spin resonance (ESR) spectroscopy. Two different regimes are observed depending on the dose range, and a correlation between the mechanical behavior of the membrane and the evolution of the concentration of the radicals in the PA fabric is observed. Globally, the porosity of the surface membrane does not vary whatever the dose may be, but the mechanical properties of the membrane as well as the permeability are strongly affected, even for low radiation dose such as 10 kGy. These results are related to chain scissions on the PA fabric, which occurred preferentially, compared to cross-linking, in the investigated dose range.     

Yb3+掺杂浓度对LaF3晶相及其上转换光谱的影响

LaF3微米晶的晶相(斜方相和六角相)及其上转换发光光谱可以通过精确调节Yb3+的摩尔掺杂浓度来控制。利用简单的水热法合成了Yb3+和Tm3+共掺杂的LaF3,YF3和NaYF4三种不同基质的氟化物纳米晶。XRD分析表明,当Tm3+的掺杂浓度不变,仅Yb3+的摩尔掺杂浓度从10%提高到20%,就可以使基质结构由六角相过渡到斜方相。实验结果表明,具有较大离子半径的稀土离子由于增强的偶极化率,更容易使电子云产生畸变,有利于基质斜方相结构的形成。     

氟化钠对雄性小鼠精子畸形的影响

为探讨氟化钠对雄性小鼠精子畸形的影响,选取50只成年雄性小鼠随机分为5组：氟化钠染毒高剂量组（34mg／kg）、中剂量组（17mg／kg）、低剂量组（8．5mg／kg）、环磷酰胺阳性对照组（50mg／kg）、生理盐水空白对照组,采用经口灌胃染毒,1次／d,连续5d,于首次染毒后的第35天颈椎脱臼将小鼠处死,取睾丸和附睾称质量,计算脏器系数;同时取附睾制片,观察精子形态,计数小鼠精子畸形率。结果表明,氟化钠染毒各组睾丸、附睾脏器系数与空白对照组比较,差别无统计学意义（P〉0．05）,染毒各组精子畸形率普遍高于空白对照组,差别有统计学意义（P〈0．001）,且随着染毒剂量的增加精子畸形率也有相应升高,呈现一定的剂量一反应关系（r=0．954,F=20．098,P〈0．05,R^2=0．909）。提示氟化钠能使雄性小鼠精子畸形率明显升高,具有一定的生殖毒性,能影响小鼠生殖功能,对小鼠生殖功能造成损害。     

氟化钠对大鼠血清微量元素的影响

为探讨氟化钠（NaF）对大鼠血清四种微量元素含量的影响,将80只2月龄SPF级SD大鼠,雌雄各半,随机分成8组：对照组[幼年（CS）、成年（AS）]和用药组[幼年高氟（CHS）、成年高氟（AHS）平订幼年低氟（CLS）、成年低氟（ALS）组,长期高氟（HS）和低氟（LS）组];对照组灌胃生理盐水,刖药组分别按相应时阃给予不同剂量的NaF灌胃。结果表明,与CS组相比,CYIS组和CLS组的P分别增加100％（P〈0．05）和193．8％（P〈0．05）;与As组相比,HS组的Ca、Zn分别下降了20．5％（P〈0．05）和40％（P〈0．05）,而P则增加了74％（P〈0．05）,LS组的Zn也下降了33．3％（P〈0．05）。提示：长期使用氟化钠可导致幼年大鼠血中化学元素代谢紊乱。