Phosphoric Acid Solution (phosphoric + acid_solution)

Distribution by Scientific Domains

Selected Abstracts

Ca for Er substitution in tetragonal ErPO4 H2O crystallised from phosphoric acid solution

R. Kijkowska
Abstract Erbium phosphate monohydrate with limited Ca for Er substitution, obtained through crystallisation from boiling phosphoric acid solution has been characterised by X-ray diffraction, Ir-spectroscopy and thermal analysis (TGA-DTA) methods. The difference in the electric charge between di-valent calcium and tri-valent erbium in the solid crystallised was compensated by simultaneous substitution of HPO42- for PO43- . Ca incorporation in erbium phosphate made expansion of tetragonal ErPO4 H2O unit cell. After ignition at 900 C the tetragonal crystal modification was maintained but the unit cell parameters of all the investigated phosphates, whether Ca-substituted or Ca-free, contracted to the same level. The unique contraction of the unit cell was resulted from recrystallisation of Ca-substituted into Ca-free erbium phosphate, while Ca was transferred into Ca(PO3)2 formed as a separate phase. ( 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Determination of fluoroquinolone antibiotics in surface waters from Mondego River by high performance liquid chromatography using a monolithic column

Angelina Pena
Abstract A novel LC,fluorescence detection method based on the use of a monolithic column for the determination of norfloxacin, ciprofloxacin, and enrofloxacin antibiotic residues in environmental waters was developed. Fluoroquinolones (FQs) were isocratically eluted using a mobile phase consisting of 0.025 M phosphoric acid solution at pH 3.0 with tetrabutylammonium and methanol (960:40, v/v) through a Chromolith Performance RP-18e column (1004.6 mm) at a flow rate of 2.5 mL/min and detected at excitation and emission wavelengths of 278 and 450 nm, respectively. After acidification and addition of EDTA, water samples were extracted using an Oasis HLB cartridge. Linearity was evaluated in the range of 0.05 to 1 ,g/mL and correlation coefficients of 0.9945 for norfloxacin, 0.9974 for ciprofloxacin, and 0.9982 for enrofloxacin were found. The limit of quantification was 25 ng/L for the three FQs. The recovery of FQs spiked into river water samples at 25, 50, and 100 ng/L fortification levels ranged from 76.5 to 91.0% for norfloxacin, 78.5 to 97.2% for ciprofloxacin, and 79.4 to 93.6% for enrofloxacin. This method was successfully applied to the analysis of water samples from the Mondego River, and ciprofloxacin and enrofloxacin residues were detected in eight water samples. [source]

Methodological assessment of acid-etching for visualizing the osteocyte lacunar-canalicular networks using scanning electron microscopy

Daniel J. Kubek
Abstract Osteocytes are the most abundant of the bone cells. Each osteocyte is contained within its own lacuna and connected to adjacent osteocytes via fillipodial processes, which form an intricate network of canaliculi within the matrix. Studying this intricate network of cells and their processes is difficult, because it exists embedded within a densely mineralized matrix. Scanning electron microscopy (SEM) has been shown to be a useful tool for visualizing this cellular network, yet the techniques involved for preparing specimens has not been systematically explored. The goal of this study was to investigate how variations in acid-etching, both etching media and etching duration, affect SEM-based visualization of the osteocyte lacunar,canalicular network. Bone samples were embedded in plastic and then acid etched in either 9% (10, 20, 40, and 60 s durations) or 37% (5, 10, and 15 s) phosphoric acid. Specimens were imaged using SEM, and qualitative evaluation of the lacunar,canalicular network was undertaken. Our findings show acid etchingwith a 9% phosphoric acid solution for 20 s provided the most favorable visualization of the osteocyte lacunar,canalicular network. Microsc. Res. Tech., 2010. 2009 Wiley-Liss, Inc. [source]

Environmental stress cracking of a chemical nature in a PBT/PBA co-poly(ester ester)

N. B. Kuipers
The Environmental Stress Cracking (ESC) of a poly(butylene terephthalate)/poly(butylene adipate) (PBT/PBA) copoly(ester ester) was studied by constant-load time-to-failure (TTF) tests performed on sharply notched tensile specimens in water and phosphoric acid solution at 353 K. For comparison, tests were also performed in air at the same temperature. It was found that the time to failure is significantly reduced both in water and in an acid solution as compared with air. ESC implies a mutual intensification of the destructive effect of loading and environment. Owing to the intrinsic hydrolytic instability of polyesters, a failure mechanism due to hydrolysis has to be excluded here to prove the ESC. Therefore the ESC test results are compared with measurements of the exclusive influence of hydrolysis on the degradation of mechanical properties. It was found that the PBT/PBA copoly(ester ester) tested is susceptible to environmental stress cracking in water and even more in a phosphoric acid solution, both at 353 K. From the comparison of the influence of water and a phosphoric acid solution on the time to failure, it was concluded that the ESC of PBT/PBA copoly(ester ester) in a phosphoric acid solution is mainly of a chemical nature. Polym. Eng. Sci. 44:1319,1327, 2004. 2004 Society of Plastics Engineers. [source]

Control of polyaniline conductivity and contact angles by partial protonation

Natalia V Blinova
Abstract Many studies require a specific value of conductivity when investigating conducting polymers. The conductivity of polyaniline can efficiently be controlled by partial protonation of the polyaniline base. Although this is a simple task in principle, practical guidelines are missing. In the present study, the changes in the conductivity of polyaniline base after immersion in aqueous solutions of various acids are reported. Polyaniline base has been reprotonated in aqueous solutions of picric, camphorsulfonic and phosphoric acids. The conductivity of partially reprotonated polyaniline varied between 10,9 and 100 S cm,1. The relation between the pH of a phosphoric acid solution, which was in equilibrium with polyaniline, and the conductivity , is pH = 0.77 , 0.64 log(, [S cm,1]). The wettability, i.e. water contact angles, can similarly be set by partial protonation to between 78 for polyaniline base and 44 for polyaniline reprotonated in 1 mol L,1 phosphoric acid. In solutions of picric acid, the transition from the non-conducting to the conducting state occurs over a narrow range of acid concentrations, and the tuning of conductivity is consequently difficult. Phosphoric acid is well suited for the control of conductivity of polyaniline because of the moderate dependence of the conductivity on the acid concentration or pH. Copyright 2007 Society of Chemical Industry [source]

Copper and cadmium extraction from highly concentrated phosphoric acid solutions using calcium alginate gels enclosing bis(2,4,4-trimethylpentyl)thiophosphinic acid

Argune Ocio
Abstract The availability of alginate gels enclosing Cyanex 302 [bis(2,4,4-trimethylpentyl)thiophosphinic acid] for the uptake of cadmium and copper from highly concentrated solutions of industrial phosphoric acid wet process phosphoric acid (WPA)] was studied. For this purpose, beads of alginate gels enclosing microdrops of kerosene solutions of the industrial extractant Cyanex 302 at different concentrations were prepared. The experimental procedure gives rise to a composite bead in which alginate is the continuous phase and the organic extractant forms the discrete homogeneously distributed phase within the bead. The equilibrium in this three-phase system (phosphoric acid,extractant solution,alginate gel) was modelled in terms of the corresponding distribution factors, the main chemical reactions and their equilibrium constants. Retention isotherms of both metal ions were obtained experimentally at four concentrations (1.0, 2.5, 5.0 and 7.5 mol L,1) of pure phosphoric acid. High metal removal efficiency, due to liquid,liquid extraction processes, was observed even in the most acidic conditions. High values of the extraction constants were estimated, with the distribution coefficients between aqueous and alginate phase being near unity. Finally, the results obtained with industrial WPA are in close agreement with those predicted by the physicochemical model developed in synthetic media. Copyright 2006 Society of Chemical Industry [source]