Potassium Bromide Disk Research Articles

Supercritical fluid extraction / capillary supercritical fluid chromatography / Fourier transform infrared microspectrometry of polycyclic aromatic compounds in a coal tar pitch

AbstractThe combination of supercritical fluid extraction, high resolution capillary supercritical fluid chromatography, and Fourier transform infrared microspectrometry is described for the separation and identification of polycyclic aromatic hydrocarbons in a coal tar pitch. The variable solvating power of the supercritical fluid was utilized to selectively fractionate the sample. The fluid extract was decompressed through a frit restrictor into the sample cavity of a cooled microvalve injector, where the analytes were deposited and concentrated for subsequent chromatographic analysis. Several of the analytes separated in the chromatograph were collected on a potassium bromide disc at a solvent elimination inter‐face for subsequent infrared analysis involving the use of an infra‐red microscope accessory. The spectra obtained show the power of this detection technique for distinguishing between isomers.

Photochemical Reduction of Ferric Oxalate in a Solid pressed Potassium Bromide Disk

Photochemical Reduction of Ferric Oxalate in a Solid pressed Potassium Bromide Disk

Optical properties of tin in the 2.5 to 40?m region

The optical constantsn andk of evaporated tin deposited on different substrates (potassium bromide and mica-sheet discs) were determined in the 2.5 to 40μm region by measuring its transmittance. From these values a second step vveacarried out to determine other physical parameters of tin films. These were the density of conduction electrons,N, the effective collision frequency of the electrons ν0 the plasma frequency, ω0, the velocity on the Fermi surface,V0 the effective area of the Fermi surface,Aeff, and the absorption coefficient,A. The energy-loss functions for surface and volume plasmons show sharp peak at 7.69μm. These values are compared with those found in earlier work.

Band-stop absorption filters for use with CO2lasers

Doped potassium bromide discs containing approximately 1% of tetramethyl ammonium halides or metal chromates are shown to be useful as band-stop absorption filters for use with CO2 lasers.

Application of I.R. Spectrophotometry in Emergency Analyses

I.R. spectrophotometry has been applied in emergency toxicological analyses. Poisons and drugs are extracted into chloroform, potassium bromide is added to the extract and the solvent evaporated. Potassium bromide discs are prepared by compression and scanned in an I.R. spectrophotometer. A data bank of standard spectra has been prepared and computerized comparison of the spectral data of the sample extract with those of authentic compounds allows the identification of toxic agents in 'real time'.

Photochemical reactions in alkali halide matrix, decarboxylation of maleic acid into ethylene by uranyl nitrate in a pressed potassium bromide disk

The feasibility of quantitative photochemical reactions of organic compounds in the solid alkali halide disk, usually used for the study of infrared spectroscopy has been explored. The disks were prepared by mixing maleic acid, uranyl nitrate and potassium bromide. Ultraviolet light was used for the irradiation of disk and the products were identified by infrared spectroscopy. It has been observed that the rate of reaction increases with the time of irradiation. The results indicate that the ethylene and uranyl (VI) complex of carboxylate are formed with the decarboxylation of maleic acid, sensitized by uranyl nitrate.

Proton-induced prompt gamma-ray spectrometry for boron analysis coupled with the potassium bromide disc method

The first page of this article is displayed as the abstract.

Infrared spectroscopic studies on polyethylene, 5. The measurement of chain branching on powder polyethylene specimens

AbstractThe scope and limitations of the potassium bromide disc technique for the infra‐red determination of chain branching in small samples of polyethylene in powder form have been assessed. Many of the samples encountered have an average particle size, prior to grinding with potassium bromide, of about 100 μm and very satisfactory results have been obtained, but the presence of larger particles leads to poor quality discs and inferior results. The well established double beam technique proves suitable for removing the interfering methylene absorption and compensation with polymethylene in the form of a film rather than as a pressed disc is preferable. Difficulties were encountered in preparing branching standards in a uniform and fine powder form, to avoid variation of the absorption coefficient of the 1 378 cm−1 methyl band with particle size. Such powders are best obtained by precipitation from solution rather than by low temperature milling. Despite these problems chain branching measurements may be made with a precision of between 5 and 10% and an accuracy of about 15%.

FLUORESCENCE ANALYSIS ON SOLID SURFACES*

Abstract— One of the recent uses of fluorescence has been in the assay of substances directly on solid surfaces such as paper chromatograms, thin‐layer chromatography (TLC) plates, potassium bromide disks, electrophoresis strips, and silicone‐rubber pads. Chromatography and electrophoresis are widely used analytical techniques and it is not surprising that fluorometric methods are used in conjunction with them. Advantages are increased sensitivity and rapidity of analysis.In this paper the use of fluorescence in the assay of substances after separation on paper and TLC chromatograms, as well as the direct assay of substances on a solid surface placed directly in a commercial fluorometer, are discussed. Particular emphasis is placed on the direct analysis of enzymatic reactions.

Characterization of naphthalene dicarboxylic acids. 2. Infrared absorption spectra

Abstract The infrared absorption spectra of the ten isomeric naphthalene dicarboxylic acids in the solid state, in potassium bromide discs, have been examined in the range 4000–250cm −1 . The spectra are sufficiently different as to allow characterization of these isomers.

Technique for the transfer o falkaloids from thin-layer plates to potassium bromide discs for spectroscopy

Technique for the transfer o falkaloids from thin-layer plates to potassium bromide discs for spectroscopy

Infrared study in potassium bromide disks of the stability and hydrolysis of aromatic polyurethane foams

Infrared study in potassium bromide disks of the stability and hydrolysis of aromatic polyurethane foams

Infrared Refractive Index of Atmospheric Aerosol Substances

The optical constants in the ir from lambda2.5 microm to 40 microm (4000-250 cm(-1)) of dry natural aerosol substances and of sea salt are presented. The aerosol substances were obtained from rain and snow water: dust and soot by sedimentation, and water soluble salts by evaporation. The spectra of the absorption index n' were derived from our published transmittance measurements of potassium bromide disks. The real part n of the refractive index was calculated from the specular reflectance at near normal incidence of disks of pure aerosol substance. The observed spectral features are being related to chemical constituents, notably sulfates and alcohol soluble organics. Optical constants of composite and wet aerosol are discussed. A simple model confirms the measured transmission of a coarse dry powder of water solubles and shows that the extinction by natural aerosol should have a minimum near 8 microm and a strong maximum near 9 microm.

The infrared spectrum of Hofmann's benzene clathrate

Unless sufficient care is taken in the preparation of Nujol mull or potassium bromide disc samples of Hofmann's benzene clathrate, partial decomposition occurs and spurious i.r. spectra are recorded.

Circular dichroism of crystalline l-cystine in potassium bromide disc. Possibility of exciton splitting

Circular dichroism (CD) of crystalline l-cystine and l-cystine dihydrochloride in a potassium bromide disc was studied to clear up the cause of the abnormal CD spectrum found for the former by Imanishi and Isemura 9, and to relate CD spectra to the conformations of disulfide groups in the crystals. Inspection of published crystalline structures showed that disulfide groups are linearly arrayed with van der Waals contacts in l-cystine crystal but not in l-cystine · 2HCl crystal. It was inferred that the abnormal CD is the result of an exciton splitting due to the characteristic array of cystine disulfides in the crystal. Supporting evidence was obtained by measurements of polarized ultraviolet and CD spectra with a potassium bromide disc in which cystine crystals were preferentially oriented in one direction. The maximum CD intensity of the longest wavelength band expected for a potassium bromide disc of l-cystine, free from exciton splitting but retaining the intact conformation, was roughly estimated. The obtained results seem to be useful to understand the CD of cystine in solution.

Ground state vibrational levels of zinc uranyl acetate

Abstract The vibrational levels in the ground state of zinc uranyl acetate [Zn(UO2)2(CH3)COO)6·H2O] have been established for the first time from the investigations of Raman, infrared and fluorescence spectra of the compound and the fluorescence spectrum has been analysed on the basis of these vibrational frequencies. The Raman spectrum has been obtained with a helium-neon laser as the excitation source. The infrared absorption spectrum has been recorded by both Nujol mull and potassium bromide disc techniques. The fluorescence spectrum has been photographed with powder samples of the compound at liquid air temperature. Besides the uranyl frequencies, eleven fundamentals due to the acetate ion and three fundamentals due to the crystal lattice have been obtained in the infrared and fluorescence spectra. Good agreement has been obtained between the values of the various fundamental frequencies from the different investigations. The interpretation given for the fluorescence spectrum confirms the analysis proposed by Dieke and Duncan involving a single electronic transition from the lowest excited state of the uranyl ion to the various vibrational levels of the ground state.

Infra-red spectra of Japanese coal: The absorption bands at 3030, 2920 and 1600 cm −1

Infra-red spectra of twelve Japanese coals, from lignite to anthracite, were measured as accurately as possible using potassium bromide discs. The absorption band at 3030 cm −1 (aromatic CH hydrogen) appears in the coal with 81.1% carbon (d.a.f.) and becomes clearer as coal rank increases. With the exception of a few coals, the absorption intensity of 2920 cm −1 (aliphatic CH hydrogen) increases gradually with rank until 86.2% carbon, but decreases sharply beyond this point. The increase in intensity at 1600 cm −1, in parallel with oxygen content suggests that oxygen-containing structures, as well as the CC aromatic structure, cause this absorption. The marked intensity of the aliphatic CH hydrogen absorption, especially at 2920 cm −1, is found to be the characteristic feature in the infra-red spectra of Japanese coals in comparison with others.

Vibrational spectroscopic studies of internal rotation of symmetrical groups. Part I. Evidence for a high barrier to internal rotation in methylpentacarbonylmanganese, CH3Mn(CO)5

Methylpentacarbonylmagnanese has been examined by i.r. spectroscopy in the vapour state, in solution, and as a solid in a potassium bromide disc. Particular attention has been paid to the antisymmetric methyl stretching vibration. Contrary to expectation on grounds of symmetry, which predicts a 12-fold barrier for internal rotation, there appears to be a high barrier of the methyl group estimated to be 2·7 ± 0·5 kcal. mole–1 in C2Cl4 solution. Intermolecular forces may also contribute to the barrier in solution, but there are indications that this is high in the vapour state also.Possible explanations for this unexpected result are considered in relation to the low-frequency vibrations of this molecule or in terms of dπ donation from metal atom to the methyl group.

Identification of Cationic Surfactants with Reineckates

As cationic surfactants are readily precipitated into reineckates, identification of 27 cationic surfactants of various types and different chain lengths were attempted with the methods of infrared spectroscopy and paper chromatography. Surfactant reineckates were prepared as follows ; 1% aqueous ammonium reineckate solution was added into 2% aqueous (or ethanol) solution of surfactants. Infrared spectra were obtained by potassium bromide disc technique, and the solvent system in paper chromatography was methanol : water : 35% hydrochloric acid (12 : 12 : 1). Surfactants used for the present experiment were separated into the following three groups ; group A : amines and quaternary ammonium salts, group B : surfactants of pyridine ring, and group C : amphoteric surfactants, which have characteristic infrared absorption bands. Each group could be differentiated and surfactants in three groups could be identified by infrared technique. Both the absorption bands of surfactants (7001, 800 cm-1) and those of reinecke ion (3, 0003, 500 cm-1) in infrared spectra of surfactant reineckates could be used in the identification of surfactants. Alkyl chain lengths could be differentiated with paper chromatography, but in this case, surfactant reineckates were treated with silver nitrate. Rf values of C12, C14, C16 and C18 except for primary amines were 0.680.78, 0.390.50, 0.170.21and 0.000.06 respectively.

Low-Temperature Grinding Technique for Infrared Analysis of Propellants and Binders in Potassium Bromide Disks

A low-temperature grinding technique for the potassium bromide pressed-disk method was developed to obtain quantitative infrared spectra of propellants and propellant binders. The effects of grinding time and temperature on the intensities of infrared absorption bands were determined. The technique was applied to the study of the thermal degradation of a polyurethane propellant.