Some fundamental considerations on analytical high-frequency plasmas.

Several possible models for plasmas, and their fundamental background, are discussed. The recent literature on investigations of fundamental plasma models and plasma parameters is reviewed.

Trace analysis by microwave excitation of sealed samples-III Determination of 0.005-25 ng of Te and 0.25-25 ng of Se in 0.5 ml of aqueous solution.

Traces of tellurium and selenium can be determined by optical emission spectrometry using microwave exitation in electrodeless discharge lamps. In 0.5 ml aqueous solution samples, freeze-dried in electrodeless discharge lamps, 10(-5) ppm Te and 5 x 10(-4) ppm Se can be determined with a relative deviation of about 20%.

Trace analysis by microwave excitation of sealed samples-II determination of 4-100 pg of Cd, In and Tl in 0.5 ml of aqueous solutions.

Trace analysis by optical emission spectrometry by microwave excitation of sealed samples has been improved by use of H(2) as a filler-gas and of BiI(3) as a matrix. It was found that the selection of suitable quartz for the manufacture of the discharge lamps is important. Limits of determination of 4 pg in 0.

The error in absorption measurements caused by the use of non-monochromatic light-III Application to linear calibration curves.

When in spectrophotometry the absorption is measured with non-monochromatic light, a curved calibration curve is often obtained. Some errors are introduced if a linear calibration curve is still used. The magnitude of these errors has been calculated.

The error in absorption measurements, caused by the use of non-monochromatic light-II Gaussian functions.

The errors in absorption measurements in spectrophotometry, caused by the use of non-monochromatic light, have been calculated. Gaussian functions have been assumed for the wavelength-dependence of the intensity of the incident light falling on the cell and the absorbance of the compound measured. Results found are similar to those found with parabolic functions.

Trace analysis by microwave excitation of sealed samples-I: preliminary investigations.

An important limitation to the sensitivity of analytical methods using atomic spectroscopy is the short residence-time of the atoms in the light-path. The possibility has been studied of sealing the samples in a quartz tube where they are forced to emit light by microwave excitation. The detection of amounts below one ng in a volume of 0.

Determination of and differentiation between cassimerite and silicate-bound tin in silicate rocks containing traces of tin.

A simple, sensitive and reproducible method is described for the determination of tin in silicate rocks at the ppm level. By applying a selective decomposition it seems possible to differentiate between tin present in the silicate lattice, in readily-accessible cassiterite (SnO(2)) and in cassiterite enclosed in the silicate. The final determination is made by extraction and photometry with phenylfluorone.

Spectrophotometric determination of 0-50 ng of chromium in 1 ml of human serum.

A method is described for the determination of chromium in 1 ml of human serum or plasma. It is based on a wet decomposition and a spectrophotometric determination with diphenylcarbazide after extraction with methyl isobutyl ketone. A 40-mm cuvette with less than 1 ml sample volume is described.

Determination of 0.01-0.1% of samarium in 40-100 mg of lead chloride.

A method is described for the determination of 5-25 mug of samarium in about 40 mg of lead chloride, based on the removal of the lead by electrolysis and determination of the samarium by extraction with PAN and measurement of the extinction of the complex at 552 nm.

The extraction constant of mercury(II) o-o'-dimethyldithizonate into toluene.

An attempt was made to determine spectrophotometrically the extraction constant of mercury(II) o-o'-dimethyldithizonate into toluene by means of a known excess of iodide as a masking agent. The results found, however, could not be explained by a simple reaction between mercury(II) o-o'-dimethyldithizonate and iodide.

Extractive spectrophotometric determination of micro and sub-micro amounts of fluoride.

A simple and sensitive extractive spectrophotometric determination of fluoride with the cerium(III)-alizarin complexan chelate has been investigated. The fluoro chelate formed is extracted into n-pentanol containing triethylamine. It is possible to achieve under selected conditions a selective extraction of the cerium(III)alizarin complexan-fluoride chelate.

The error in absorption measurements, caused by the use of non-monochromatic light-I Parabolic functions.

The errors in absorption measurements in spectrophotometry, caused by the use of non-chromatic light, have been calculated. Parabolic functions have been assumed for the wavelength-dependence of the intensity of the incident light falling on the cell and of the absorbance of the compound measured. Results of the calculations may be used to predict non-linearity of absorbance-concentration curves or photometric titration curves.

The volumetric determination of nitrite with chloramine T.

Nitrite may be determined by oxidation with chloramine T, reaction of the excess of chloramine T with excess KI, and titration of I(2) formed, with thiosulphate. The reproducibility and some interferences are discussed.

Rapid iodometric determination of copper in some copper-base alloys.

Copper-base alloys, especially those containing tin, are readily dissolved in a mixture of hydrofluoric and nitric acids. In the resulting solution copper can be titrated iodometrically in the conventional manner.