Titrimetric microdetermination of silver, lead and cadmium with thioglycollic acid and of mercury(II) with 2-mercaptopropanoic acid

A simple and rapid titrimetric method is described for the microdetermination of Ag(+), Cd(2+) and Pb(2+), based on their formation of mercaptides with a measured excess of 2-mercaptopropanoic acid, and similar determination of Hg(2+) with thioglycollic acid. Univalent and bivalent metal ions release one and two thiol protons respectively, which along with the carboxyl protons of the thiol reagent are titrated with standard alkali. The difference from the blank titration gives the increase in acidity which is a function of the metal-ion concentration. The proposed procedure is applicable to samples containing 0.025-0.25 mmole of these ions, the average deviation being in the range 0.2-0.5%.     

Metal ion doped polymers as media for optical memories

Polymer materials are making an impact on optical storage technology to develop high information density and fast access type memories with a high read-out efficiency. The principle and advantages of three-dimensional (3-D) data storage in the form of interference patterns (holograms) have been outlined. Three different information storage materials have been developed by doping metal ions such as Cr(VI) and Fe(III) in water-soluble polymers, namely poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA), which need no further thermal or chemical treatment. Volume transmission holograms have been recorded in dichromated poly(vinyl alcohol) (DCPVA), ferric chloride doped poly(vinyl alcohol) (FePVA) and dichromated poly(acrylic acid) (DCPAA), with and without an electron donor (dimethyl formamide), and xanthene dyes (fluorescein, eosin Y and Rose Bengal). Different parameters influencing the holographic performance have been optimized to achieve a high real-time diffraction efficiency (～70%). An electron transfer process from the polymer matrix to Cr(VI)/Fe(III), leading to the photocrosslinking of the polymer in the form of an interference pattern, has been suggested as the mechanism of information storage (hologram recording) in these materials.     

萘油制备新型水煤浆添加剂的研究

研究了如何利用萘油中的有效成分合成出性能良好的水煤浆添加剂。通过合理的正交试验设计和多元线性回归分析方法得到了合成萘油添加剂的较佳工艺条件,即在75 g的萘油中,加入浓H2SO4 30 mL,在160 ℃时磺化2 h;加入HCHO 25 mL,在105 ℃时缩合1.5 h。利用实验合成的萘油添加剂与纯萘磺酸甲醛缩合物作添加剂分别对庞庄煤进行制浆实验。结果表明,萘油添加剂性能良好,可显著降低萘油添加剂的成本。应用傅立叶变换红外光谱对萘油添加剂的结构进行了分析,测出萘油添加剂主要为含有－CH2－,－SO3－等基团的芳香族化合物。对萘油添加剂改善水煤浆性能的作用机理进行了初步探讨。     

A controlled-release anti-inflammatory drug

A procedure to obtain a controlled-release microencapsulated anti-inflammatory drug based on a solvent evaporation method is described. The present method makes use of ethylcellulose as the polymer and methylene chloride as solvent. The evaporation of solvent is controlled by means of an air stream. Variations in the preparative procedure and their effects on capsule dimensions and permeabilities were studied. The release behavior of the drug is determined, and two different diffusion constants are also determined: 7.0×10⁻¹⁰ cm²/s and 1.2×10⁻¹⁰ cm²/s, corresponding to low and high release time. Based on these results it is proposed that these microcapsules have a nonhomogeneous polymeric wall, and are more porous in the outer surface. This model might be applicable to the microcapsules obtained by means of the solvent evaporation method.     

Summary of ISO/TC 201 Standard: XXIX. ISO 20903: 2006—Surface chemical analysis—Auger electron spectroscopy and X‐ray photoelectron spectroscopy—methods used to determine peak intensities and information required when reporting results

This article is a brief summary of the ISO Standard 20903. This standard provides information on methods for the measurement of peak intensities in Auger electron and X‐ray photoelectron spectra and on uncertainties of the derived peak areas. It also specifies the necessary information required in a report of analytical results based on such measurements. Published in 2007 by John Wiley & Sons, Ltd.     

A study of adsorption characteristics of traces of chromium(III) and (VI) on selected surfaces

The adsorption losses of chromium(III) or (VI) on the walls of Pyrex, flint glass and polyethylene beakers have been investigated. Chromium(III) or (VI) solutions were stored in beakers at different hydrogen ion concentrations, and losses due to adsorption were measured at various contact times by counting the γ-ray activity from chromium-51 radiotracer. At pH 6.95, chromium(III) solutions showed the greatest instability, particularly in polyethylene beakers, where losses up to 25% were observed at the end of the 15-day contact period. Chromium(VI) showed a completely different pattern; losses less than 1% were observed at the end of 15 days on all the three types of containers.     

流动注射-氢化物发生-原子吸收光谱法测定香烟接装纸中的痕量铅

研究了流动注射-氢化物发生-原子吸收光谱法测定香烟接装纸中铅含量的分析方法.讨论了氢化物发生的最佳条件,方法的回收率为95%～104.5%,检出限可达0.22 ng/mL,线性范围在0～50 ng/mL,线性回归方程为y=0.012x 0.0106,相关系数γ=0.9997,相对标准偏差在1.2%～3.3%.     

The crystal structure of a tricarbonyliron-substituted cyclobutadiene complex: Tricarbonyl[1,2,2a,12a-η-5,10-dimethyldibenzo[a,c]cyclobuta[f]cyclooctene-3,12-dione] iron

The crystal structure of tricarbonyl[1,2,2a,12a-η-5,10-dimethyldibenzo[a,c] cyclobuta[f] cyclooctene-3,12-dione] iron, C₂₀O₂H₁₄Fe(CO)₃, has been determined by the single crystal X-ray diffraction technique using data collected with a fully automated diffractometer. The unit cell is monoclinic, space group P2₁/c with a = 12.025(2), b = 23.204(3), c = 14.614(2) Å, β = 102.16(2)°, and contains eight molecules (two per asymmetric unit). The structure was elucidated to study the coordination of the iron atom and to correlate the conformation of the eight-membered ring with an NMR study. The final structure was obtained by Patterson-superposition and Fourier techniques and refined by full-matrix least-squares to a crystallographic residual of 0.070. In both independent molecules the iron atom is 1.77 Å from the cyclobutadiene ring to which it is coordinated. The eight-membered ring is flattened from a boat conformation and the six-membered rings are twisted from coplanarity by an angle of 74°. The twist is such that if one ring points above the eight-membered ring, the other ring will point below it with concomitant pointing in the opposite sense by neighboring carbonyl groups. Such a structure has conformational chirality. It is postulated that the stability of each enantiometer is due to the particularly high energy of the transition state through which each would pass to achieve inter-conversion.     

ALTERNATE PREDOMINANCE IN COMPETITION FOR CONJUGATION IN NITROGEN BRIDGE COMPOUND

It is demonstrated quantitatively that the serial number N is not m + n + 4 in the nitrogen bridge conjugated system (Ⅸ), so the lone pair of electrons on the nitrogen cannot conjugate with acenyl branch and formyl polyenic branch simultaneously. The character of UV spectra and substituent equivalents (△Ns) show that acenyl branch competes for the lone pair of electrons with formyl polyenic branch. If the length m of acenyl branch is lengthened while n keeps constant, a point where the acenyl branch is predominant over formyl polyenic branch in competition, will eventually be reached. On the other hand, the effect of the latter will become greater than the former. The effect of the two branches predominates each other alternately with the alternate increase in m and n values.     

Applications of capillary gas chromatography in routine toxicological analyses

Capillary columns offer the toxicologist several advantages over packed columns. We have presented a highly reproducible screening procedure based on the retention index system and have shown the use of capillary columns for routine quantitation. We are currently expanding the use of these columns in our laboratory and predict that they will be in routine use by most toxicologists in the near future.