Crystallization behavior of binary metallic glasses containing Pt

Binary MPt glasses were made by rapid quenching from liquid, where M is Ti, Zr, and Hf. Glass forming compositions were found near eutectics in TiPt, ZrPt and HfPt. Isothermal crystallization for Zr₇₅Pt₂₅ was studied at a temperature range from 780 to 792 K. The non-isothermal transformation was measured by differential scanning calorimetry with heating rates from 5 to 160 K/min. Activation energy for crystallization was obtained from the non-isothermal heating, which is consistent with that from the isothermal annealing.     

Simple semiquantitative determination of trace metal ions by use of reagent gel columns-II: determination of zinc with dithizone gel

Zinc(II) at the sub-ppm level was determined by using a column, packed with gel beads containing dithizone. The beads turned from green to pink when the sample solution containing zinc was passed through the column at pH 6.2. Various interfering cations were masked by the combined use of sodium thiosulphate, alpha'alpha-bipyridyl, hydroxylamine hydrochloride, N,N'-bis(beta-hydroxyethyl) dithiocarbamate and beta-dithiocarbaminopropionic acid. The length of the pink zone was proportional to the amount of zinc in the sample. With 0.01% dithizone gel, as little as 0.01 ppm of zinc could be determined in a 10-ml sample at a flow rate of 0.2 ml min .     

The solvent-initiated photolysis of dichloro(2,2'-bipyridine)platinum(II) in chloroform

Under 254 nm irradiation, [Pt(bpy)Cl2] is converted to [Pt(bpy)Cl4] in a solvent-initiated process. The reaction is very nearly zero order throughout. The rate decreases slightly with increasing starting concentration. These characteristics can be rationalized by a rate law of the form afs, where fs is the fraction of light absorbed by chloroform. The species that reacts with [Pt(bpy)Cl2] is believed to be CCl3OO.     

Simple semiquantitative determination of trace metal ions by use of reagent gel columns-I: determination of mercury with dithizone gel

Mercury(II) at the sub-ppm level was determined by using a column packed with gel beads containing dithizone stabilized as the zinc complex. The beads turned from pink to green when the acidified sample solution was passed through the column. If the solution contained mercury (II), the colour of the gel beads turned to orange owing to the formation of mercury dithizonate. The length of the coloured zone was proportional to the amount of mercury in the sample. With 0.01% dithizone gel, as little as 0.1 ppm of mercury(II) could be determined in a 20-ml sample at a flow-rate of 1 ml/min.     

Doubly excited 2 1Delta g state of Na2

The doubly excited valence (3p+3p) 2 (1)Delta(g) state of Na(2) is experimentally observed by using optical-optical double resonance spectroscopy. A single line Ar(+) laser (a total of nine lines) was used to pump the sodium dimers from thermally populated ground state X (1)Sigma(g) (+) to the intermediate B (1)Pi(u) state. Then, a single mode Ti:sapphire laser was used to probe the doubly excited 2 (1)Delta(g) state. Violet fluorescence emitted from the highly excited states (mainly 2 (3)Pi(g) or 3 (3)Pi(g) states which are transferred from 2 (1)Delta(g) state via collision) to the a (3)Sigma(u) (+) state was monitored by a filtered photomultiplier tube (PMT). A total of 582 rovibrational levels of 2 (1)Delta(g) state were observed, identified, and assigned to the vibrational and rotational quantum numbers in the range of 0< or =v< or =28 and 11< or =J< or =99, respectively. The absolute vibrational quantum number assignment was verified by comparing the totally resolved fluorescence with the calculated Franck-Condon factors between 2 (1)Delta(g) state and B (1)Pi(u) state. Dunham coefficients and Rydberg-Klein-Rees potential curve were derived from these observed quantum levels. The primary molecular constants of Na(2) 2 (1)Delta(g) state are T(e)=32 416.759(15) cm(-1), omega(e)=124.8484(36) cm(-1), B(e)=0.119 158(3) cm(-1), and R(e)=3.508 20(5) A.     

Chiral analysis of baclofen by alpha-cyclodextrin-modified capillary electrophoresis and laser-induced fluorescence detection

An enantioselective method for baclofen (4-amino-3-p-chlorophenylbutyric acid) based on capillary electrophoresis (CE) separation and laser-induced fluorescence (LIF) detection has been developed. Naphthalene-2,3-dicarboxaldehyde (NDA) was used for precolumn derivatization of the nonfluorescent drug. alpha-Cyclodextrin (alpha-CD) was included in the buffer as a chiral selector for the separation of NDA-labeled S-(+)- and R-(-)-baclofen. Optimal resolution and detection were obtained with an electrophoretic buffer of 50 mM sodium borate (pH 9.5) containing 7 mM alpha-CD and a He-Cd laser (lambda ex = 442 nm, lambda em = 500 nm). Combined with a simple cleanup procedure, this method can be applied to the analysis of baclofen enantiomers in human plasma. The relative standard deviation (RSD) values on peak areas of a plasma sample containing 1.0 microM racemic baclofen were 6.4 and 4.9% (n = 8) for the S-(+)- and R-(-)-enantiomer, respectively. The RSD value on migration times of both enantiomers was 0.5% (n = 8). Calibration graphs for S-(+)- and R-(-)-baclofen in plasma showed a good linearity (r > or = 0.999) in the concentration range of 0.1-2.0 microM. The limit of detection of baclofen in plasma was about 10 ng/mL.     

Styrene emulsion polymerization: Kinetics and particle size distributions in highly swollen latex systems

The results are reported of studies on the kinetics and the time evolution of the particle size distribution in seeded styrene emulsion polymerization systems wherein the seed latex particles were highly swollen with monomer as a result of prior swelling by dodecane. Conditions were such that no new latex particles were formed nor was a significant number of monomer droplets present (“Interval III”). The data were fitted to obtain values for the rate coefficients for entry and exit (desorption) of free radicals. It was found that, during the early part of the polymerization (when the polymer:monomer ratio in the latex particles is considerably less then in an equivalent emulsion polymerization system without dodecane), the entry rate coefficient was much smaller than that measured in systems without dodecane. This effect is consistent with an entry mechanism wherein entering free radicals must displace surfactant molecules from the latex particles.