Spectrochimica Acta最新文献

The details of the construction of a cell for the measurement, in the gase phase, of IR absorption spectra of crystalline substances is described. The cell can be evacuated to 10⁻⁵ mm Hg, heated to 250°C, and is equipped with interchangeable windows; its volume is approximately 100 ml and the optical path is 10 cm. The measurable quantity of substance is on the order of a few tens of milligrams and the substance is quantitatively recovered in a pure state after the measurement. Some problems posed by the functioning and the maintenance of the cell, as well as the advantages of the method, are discussed.

The infrared spectra of 1,2,5-thiadiazole and 1,2,5-thiadiazole-d₂ in the gaseous and liquid states, have been measured between 4000 and 400 cm⁻¹. The Raman spectrum of liquid 1,2,5-thiadiazole has also been obtained. An assignment of all the infrared active modes was based on the rotational envelope contours of the gas phase spectra, the isotope shift and the polarization measurements of the Raman spectrum. The two infrared inactive but Raman active A₂ modes were not detected.

Infra-red absorption spectra of 15 coordination compounds of pyridine with Pt, Rh and Ir have been observed between 100 and 3200 cm⁻¹; in some cases ultra-violet and Raman spectra have also been observed. The influence of co-ordination on the vibration spectrum of pyridine, the structure of the co-ordinated units and the differences in the spectra of cis-trans isomers are discussed.

In cyclic compounds, and others containing NPN groups, ν_PN is assigned to the region 1170–1438 cm⁻¹. In compounds in which resonance hybrids involving PN appear unlikely ν_PN is found in the range 1325–1400 cm⁻¹. It is suggested that this upper limit would be exceeded in compounds of this type containing fluorine substituents.

The literature assignments for PN bonds are discussed and it is suggested that this bond is best identified by indirect correlations. Such correlations are described for PNH₂, PNHR, PNR₂,

The infra-red spectrum of o-bromotoluene has been investigated in liquid phase in the region 700–4590 cm⁻¹. Assignments of the observed frequencies have been proposed by assuming C_s symmetry for the molecule.

The far infra-red spectra of K₂PtCl₄, K₂PdCl₄ and K₂PtCl₆ have been measured in the frequency region from 500 to 600 cm⁻¹ and a normal co-ordinate treatment has been made for these compounds on considering the lattice vibrations. It has been shown that the modified Urey-Bradley force field is adequate for K₂PtCl₄. The potential functions between K⁺ ion and Cl atom has been discussed.

The infrared spectra of nine diphosphine disulfides, R₂P(S)P(S)R₂, have been recorded in the 250–1200 cm⁻¹ range both in solution and in the solid state. Some Raman data is reported for the tetramethyl, tetra(ethyl), and tetra(n-butyl) compounds. The most satisfactory interpretation of the data is that all the compounds exist in the trans (C_2h) conformation of the diphosphine disulfide structure in the solid state. The PS antisymmetric stretching frequency was found to have a similar dependency on the nature of the substituents to that reported for tertiary phosphine sulfides. The infrared spectrum of tetraphenyldiphosphine is also reported.

Using high-brightness lamps and a hydrogen—air flame, the determination of tin is as convenient as any other atomic absorption analysis. High-brightness lamps increase the emission of the 2246 Å resonance line about seventy times. Hydrogen—air flames increase the sensitivity over acetylene—air flames about 2·5 times. Tin sensitivity is about 1 ppm for 1 percent absorption and the detection limit is about 0·1 ppm in a water solution. Several National Bureau of Standards (NBS) metallurgical samples were analyzed for tin.