Conditions for attainment of thermodynamic equilibrium for the Ag/Hg system

Following a previous study on the influence of the size of silver particles used in dental alloys on the conditions for the attainment of thermodynamic equilibrium, results are presented on the influence of the particle shape factor. Calorimetric results obtained using different particle forms are compared with those derived from a mathematical model in which it is considered that silver particles can assume a spherical or cylindrical (flat or narrow) shape. It appears that the thermal effects obtained by computation are closer to those obtained by calorimetric experimentation when the sphere of the model is transformed into either a disc or a rod.     

Comparing columns for gas chromatography with the two-parameter model for retention prediction

The retention times of selected compounds in temperature programmed gas chromatography were predicted using a two-parameter model, on the basis of thermodynamic data obtained from isothermal runs on seven capillary columns, primarily substituted with 5% diphenylsiloxane. The scope for using thermodynamic data obtained from isothermal runs on one column to optimize separation on a different column or a different instrument setup was investigated. Additionally, the predictive utility of thermodynamic data obtained using a DB-5 column that had been in use for three years was compared to that of a new column of the same model. It was found that satisfactory separation could be achieved on one capillary column or instrument setup on the basis of thermodynamic data obtained using a different column or instrument set-up.     

Synthesis of 2-propyloxazole and 2-propyloxazole-4-carboxylic acid derivatives

2-Propyloxazole (VI) was obtained in a number of steps starting from butyronit rile. The hydrazide and amide were obtained from ethyl 2-propyloxazole-4-carboxylate; the amide was converted to the nitrile, from which the thioamide and amidoxime were obtained by the usual method. Attempts to convert VI to 2-propylisonicotinic acid or its nitrile by the reaction of VI with acrylic acid or acrylonitrile did not give positive results.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 7–9, January, 1972.     

PECVD of SiOxNyCzHw thin films from hexamethyldisilazane containing feed. Investigation on chemical characteristics and aging behavior

The chemical characteristics and aging behavior of thin films obtained by HMDSN/NH₃ or N₂ containing plasmas have been studied by means of FT-IR spectroscopy as a function of feed composition, substrate temperature and bias voltage. Deposits obtained with low energy ion bombardment are polyphasic and contain a consistent fraction of polysilazane. Reactive polymeric SiH₂ chains are formed when ammonia or nitrogen are added to the feed. Film aging is mainly due to the reactions of Si-H bonds and of linear polysilazane chains. Films with better stability are obtained by excluding ammonia or nitrogen from the feed and with bias superimposition.     

Synthesis of Reactive-Ended Acrylic Polymers by Group Transfer Polymerization: Initiation with Silyl Ketene Acetals

Living methacrylate polymers are obtained at room temperature and above by initiation with ketene silyl acetals in the presence of a soluble bifluoride catalyst. During the polymerization, a trialkylsilyl group is transferred from the living chain end to incoming monomer. The new procedure has thus been named group transfer polymerization (GTP). Monodisperse polymers with predetermined molecular weights as high as 100,000 can be obtained by adjusting the monomer/initiator ratio. Telechelic poly(methyl methacrylate) with hydroxy or carboxy ends can be obtained by using an initiator containing a protected hydroxy or carboxy group and coupling the resulting living polymer.     

Synthesis of thiazole aminophosphine oxides, aminophosphonic and aminophosphinic acids and Cu(II) binding abilities of thiazole aminophosphonic acids

A series of new aminophosphine oxides, aminophosphonic and aminophosphinic acids derived from thiazole was synthesized by addition of phosphine oxides or silylated phosphorus esters to the corresponding thiazole aldimines. The thiazole aldimines were obtained from 2-thiazole aldehyde and primary amines by a standard procedure. The corresponding phosphine oxides were obtained by alkylation of diethyl phosphite or ethyl phenylphosphinate with the appropriate Grignard reagents. The silylated phosphorus esters were prepared from trimethyl phosphite and from methyl- or phenylphosphinic ethyl ester by treatment with bromotrimethylsilane. The coordination ability towards Cu(II) ions are described for two obtained aminophosphonate ligands.     

Molecular weight distribution of poly-N-vinylcarbazole obtained in catalytic solid-state polymerization

The molecular weight distribution of poly-N-vinylcarbazole (PVCar) obtained in solid-state polymerization with various catalysts or γ-rays was measured by gel-permeation chromatography, in order to determine the mechanism of the solid-state polymerization. In addition, the molecular weight distribution of PVCar obtained in the solution polymerization by the cationic catalyst was also measured. The molecular weight distribution of PVCar obtained in the catalytic solid-state polymerization was broad and had three peaks, independent of the nature of catalysts, radical and cationic. A large amount of low molecular weight oligomer (probably dimer or trimer) was formed in the catalytic solid-state polymerization of VCar. The molecular weight distribution of PVCar obtained in the cationic solution polymerization showed only one sharp peak. On the other hand, the molecular weight of PVCar obtained in the radiation-induced solid-state polymerization was larger than that obtained in the catalytic solid-state polymerization, and dimer or trimer was not formed. The molecular weight distribution of PVCar obtained was composed of one sharp peak in the high molecular weight region, and a broad peak in the low molecular weight region, and was extremely different from that of PVCar obtained in the catalytic solid-state polymerization.     

Obtaining structural information on perfluorocarbons by mass spectrometry II-charge-exchange method

Structural and molecular ion information on perfluorocarbons (PFCs) can be obtained by charge-exchange reactions of nitrogen or oxygen radical cations with PFCs; such information usually cannot be obtained by the electron impact or negative ion chemical ionization methods. Charge-exchange reactions occurred when 0.5-1.0 Torr (1 Torr as 133.3 Pa) of nitrogen, air or other gases was introduced into the chemical ionization source of a mass spectrometer, with electron energies ranging from 55 to 230 eV. Changing the repeller voltages and electron energies had little effect on the appearance of charge-exchange mass spectra of PFCs. However, when air or nitrogen was introduced in the direction opposite to sample flow, more intense molecular ions and/or higher mass fragment ions were obtained at the cost of a small loss of sensitivity. The charge-exchange mass spectrum of perfluoro-1,3-dimethyladamantane is very similar to the high-energy collisionally induced dissociation spectrum of its molecular radical cation. This technique provides an important validation tool without the use of tandem mass spectrometry for the structure determination of PFC isomers.     

Partial molar volumes of organic solutes in water. VI.o-Chlorophenol andp-chlorophenol at temperatures from 298 K to 573 K and pressures up to 30 MPa

Density data for dilute aqueous solutions of two isomeric chlorohydroxybenzenes (chlorophenols) obtained in the temperature range 298.15 K to 573.15 K and at either atmospheric pressure, or at pressures close to the saturated vapour pressure of water, and at pressures up to 30 MPa are presented together with partial molar volumes calculated from the experimental data. The data were obtained using either a high-temperature and high-pressure flow vibrating-tube densimeter for measurements at elevated pressures or a commercial vibrating-tube cell DMA 602HT for measurements at atmospheric pressure.     

Ceramic Films via Organometallic Complex as Single Source Precursor

Fe2(CO)6(μ-S2) was used as a single source precursor in attempt to produce FeS film via MOCVD. Pyrolysis of Fe2(CO)6(μ-S2) at temperature below 500℃ produced Fe1-xS or Fe7S8 powder as indicated by its powder X-ray spectra. At 750 ℃, polycrystalline FeS powder was obtained. In film deposition, polycrystalline Fe1-xS or Fe7Ss films were obtained on Si(100) and Ag/Si(100) substrates below 500 ℃. SEM micrographs showed the film on Si(100) substrate containing whisker like grains. However, pillar like grains were obtained on Ag/Si(100) substrate.Deposition rates are also different for different substrates as evaluated by the thickness of the films, which were obtained by SEM micrographs of the cross section of the films. At 750℃, similar polycrystalline Fe1-xS or Fe7S8 film was obtained.     

Problems and risks occurred during uncertainty evaluation of a quantity calculated from correlated parameters: a case study of pH measurement

Parameters of a model describing a measurement process obtained during a calibration experiment allow one to calculate a measurement result, but a simple estimation of measurement uncertainties of the parameters is not sufficient to assess the uncertainty of the result. In this paper, an example of a pH measurement conducted using an ion-selective electrode is presented, in which the uncertainty is evaluated taking into consideration the existing correlation between the parameters of the electrode. The calculations apply either covariances or correlation coefficients that have to be computed additionally. The example presented in this paper illustrates that there are some problems with rounding of variables which, because of the existing very strong correlations, significantly changes the sought uncertainty. This approach is compared with other approaches, that is, usage of uncorrelated variables and Monte Carlo simulations that are described in an earlier work. It is concluded that the approach of uncertainty evaluation, in which covariances or correlation coefficients are explicitly calculated, is work-consuming and may cause significant discrepancies between correct and obtained assessments if some roundings or approximations are done, or if the correlation coefficient is obtained experimentally based on data including random errors.     

Epimination of olefins by means of 3,3-pentamethyleneoxaziridine — A one-step synthesis of aziridines

3,3-Pentamethyleneoxaziridine, which is readily obtained by treatment of cyclohexanone with ammonia and sodium hypochlorite or hydroxylamine-O-sulfonic acid, reacts with olefins with transfer of the NH group to give aziridines. Aziridines were obtained from styrene, ring- or side-chain-substituted styrenes, norbornene, and acrylonitrile in 20–70% yields. Cyclohexene is doubly aminated to give N-aminoaziridine. Nitriles are formed from phenylacetylene and diphenylacetylene as a result of rearrangement.     

The heterometric microdetermination of mercury of mercaptobenzthiazole

The heterometric determinations of murcury or mercaptobentlnazole are very sensitive reactions. An aqueous or a dilute alcoholic solution is used and the titration may lie carried out at pH 2–10. If meicaptobenzlhiazole is determined, two analytical end-points are obtained : the first gives an estimate, the second gives the precise end-point. In all cases, the insoluble Hg(MBT)₂ is obtained, The presence of larger amounts of strong acids is disadvantageous Large amounts of acetic acid cause distuibances in aqueous solution; dilute alcoholic .solution is therefore used The theoretical end-point is obtained by the intersection of two lines. In acid solution a horizontal maximum density line is obtained at the end ot the reaction, in alkahne solution a maximum point is obtained instead. 1–2 mg mercury or meicaptobenzthiazole may be determined in 20–30 ml solution with an error of 0–3% 'Ihe titration time is 10–20 mniutes     

The non-destructive identification of solid over-the-counter medications using single particle aerosol mass spectrometry

Single over-the-counter medication tablets were analyzed in real time using Single Particle Aerosol Mass Spectrometry (SPAMS). Dual-polarity time-of-flight mass spectra were obtained for micrometer-sized single particles dislodged from a single tablet without destroying the shape or markings of each tablet. The solid tablet was placed in a modified-top glass vial and shaken to dislodge and introduce micrometer-sized particles into the SPAMS system. Unique spectra from these particles were obtained in less than 1 s for single tablets of aspirin, ibuprofen, pseudoephedrine, phenylephrine, loratadine, or diphenhydramine. The signals obtained allowed the non-destructive identification of an individual tablet in seconds. SPAMS presents an ideal system for high-throughput analysis of solid drugs.     

Synthesis and Photoreaction of a-Methylene-γ-Butyrolactone-Psoralen Heterodimers

Three double-headed molecules were synthesized by linking a photoreactive linear (1, 2) or angular (3) furocou-marin via a linear 10- or 5-carbon chain to an electro-philic α-methylene-γ-butyrolactone. The photochemical behavior of these molecules was investigated in ethanol at 365 nm and the photocycloadducts obtained from each compound were isolated and characterized. In all cases, the photoreactivity results showed the 3,4-pyrone double bond of the psoralen (linear or angular) to be the most reactive and [2 + 2] intramolecular photocycloadducts between the 3,4-pyrone and the exomethylenic double bonds were obtained. With compounds 1 and 2, two kinds of intramolecular photocycloadducts were obtained, namely cissyn-exo derivatives in 46% and 36% yield, respectively, and trans-syn-exo derivatives in 14% and 18% yield, respectively. With compound 3, only the trans-syn-exo derivative was obtained in 33% yield.     

The study of macronet isoporous styrene polymers by gel permeation chromatography

Gel permeation chromatography was used for studying the structure of macronet isoporous styrene polymers swollen in chloroform. The polymers were obtained by crosslinking polystyrene either in a solution or in a swollen state using monochlorodimethyl ether and p-xylylenedichloride via the Friedel–Crafts reaction. It is shown that the networks obtained by structurization of concentrated polystyrene solution in a good solvent are characterized by loose structure, fine pores (ca. 10 Å), and narrow pore distribution. In poor solvents or in strong dilution of polystyrene and at the instant of net formation, the polymers that are obtained contain, in addition to fine pores, large pores with diameters up to 300 Å.     

"Mix and shake" method for configurational assignment by NMR: application to chiral amines and alcohols

[reaction: see text] A new methodology for determining absolute configurations by NMR in just a few minutes is presented. The required derivatives are obtained by mixing a solid matrix-bound auxiliary reagent (MPA, MTPA, or BPG) with the chiral substrate (primary amines or secondary alcohols) directly in the NMR tube. The NMR spectra of the derivatives are obtained without any type of separation, workup, or manipulation. The use of a 1:2 (R)/(S)-MPA resin permits the configurational assignment to be carried out with just one spectrum.     

Analytical approximation of the gamma ray spectra from germanium detectors

Several functional forms for shape function are tested using data obtained by a Ge(Li) detector. A function built from a Gaussian, a step function and a symmetric or asymmetric tailing on a linear or polynomial background is needed. A new shape function is proposed and superior fit are obtained.     

New high-yield,one-step synthesis of polyglycolide from haloacetic acids

In a new, one-step synthesis, polyglycolide was prepared by the reaction of bromo- or chloroacetic acid with triethylamine in a nitromethane solution. It was discolored, by iodoacetic acid possibly as a result of iodine formed by the decomposition of triethylammonium iodide. The structure of polyglycolide was characterized by hydrolysis, ¹H-NMR and IR spectra, and x-ray powder diffraction, which indicated partial crystallinity. A mechanism is proposed for the formation of polyglycolide. A lower limiting value of the number-average molecular weight of 10⁴ was determined by cryoscopy in 1,3-dinitrobenzene for polyglycolide prepared from bromoacetic acid; the measurement was inaccurate because of the low solubility of the polymer. No significant effect of solvent (acetone, ether, or chloroform) on yield or melting point was observed; a higher yield was obtained in nitromethane. The polymer obtained with tri-n-propylamine and bromoacetic acid had properties similar to that obtained with triethylamine. No polymer was obtained with N,N-dimethylaniline and bromoacetic acid or with triethylamine and bromoacetic acid in aqueous solution.     

Study of nano-emulsion formation by dilution of microemulsions

The influence of different dilution procedures on the properties of oil-in-water (O/W) nano-emulsions obtained by dilution of oil-in-water (O/W) and water-in-oil (W/O) microemulsions has been studied. The system water/SDS/cosurfactant/dodecane with either hexanol or pentanol as cosurfactant was chosen as model system. The dilution procedures consisted of adding water (or microemulsion) stepwise or at once over a microemulsion (or water). Starting emulsification from O/W microemulsions, nano-emulsions with droplet diameters of 20 nm are obtained, independently on the microemulsion composition and the dilution procedure used. In contrast, starting emulsification from W/O microemulsions, nano-emulsions are only obtained if the emulsification conditions allow reaching the equilibrium in an O/W microemulsion domain during the process. These conditions are achieved by stepwise addition of water over W/O microemulsions with O/S ratios at which a direct microemulsion domain is crossed during emulsification. The nature of the alcohol used as cosurfactant has been found to play a key role on the properties of the nano-emulsions obtained: nano-emulsions in the system using hexanol as cosurfactant are smaller in size, lower in polydispersity, and have a higher stability than those with pentanol.