Heather J. Bowley

Quantitative determination of thiourea in aqueous solution in the presence of sulphur dioxide by Raman spectroscopy

A method has been developed for the quantitative determination of thiourea in aqueous solutions acidified with sulphuric acid in the presence of sulphur dioxide. The method uses laser Raman spectroscopy and is valid in the presence of high concentrations of sulphur dioxide and inorganic salts. This is particularly important with respect to the use of such solutions for the leaching of gold from ores and concentrates. The method is simple, rapid and accurate to within ±1.2% and has been applied to the study of solutions used in leaching experiments.

Some insights into the microstructure of polypyrrole

Abstract Estimation of the molecular weight between crosslinks and determination of the average conjugation length in polypyrrole are reported. By applying the Flory equation to dimethylsulphoxide-swollen dedoped polymer, it was found that the molecular weight between crosslinks is larger than previously thought and lies in the range of 25–65 pyrrole units. U.v. and resonance Raman spectroscopy indicate that the average conjugation length is short. The upper limit is about 6 pyrrole units.

Instrumentation for Raman Spectroscopy

In general terms the instrumentation required to undertake Raman spectroscopic studies is extremely simple. We require the following: 1. Some means of holding or containing the sample to be analysed. 2. A light source (laser). 3. A collection optic to collect the Raman scattered photons. 4. A monochromator to separate the Raman signal into its constituent wavelengths. 5. A detector to detect the photons at the various wavelengths where the Raman signal is produced by the sample and to give an output which is a measure of the relative intensities of the signals at these different wavelengths. 6. A computer system to make optimum use of the photons collected and to store and display the spectra.