Using a single-beam spectrophotometer (e.g. Spec 20) to obtain a spectrum.

145. Descriptions of an "easy-to-use iterative" method to reinforce concepts in equilibrium that use spreadsheets. Article includes examples of data, advantages and limitations of the method, and suggests sample problems for use with this method.

Multiple scans are conveniently accumulated using the multiscale mode of a multichannel analyzer. Isotopic abundances with average relative % errors on the order of 5% have been obtained to illustrate the improvement in precision that is possible with time averaging. Enhancement of sensitivity is also shown. Application to multielement analysis is demonstrated. No significant resolution loss is observed during the multiple scan averaging.

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Problems with the treatment of data from the study of both exothermic and endothermic ion-molecule reactions are discussed. Recommendations are (i) to extrapolate data from an obviously linear region in the plot of ratios of secondary to primary ion intensity which appears -1-3 V above the value of the onset potential; (ii) to use ionization methods that give low internal energies to primary ions; (iii) to set for moderately high resolution; (iv) to check the stability of the primary ion current frequently; (v) to pay special attention heed to source and collision region pressure stability; and (vi) to keep collision region pressures below 0.6 mPa.