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Acidic Potassium Dichromate Solutions as Ultraviolet Absorbance Standards.
1Institute for Materials Research, National Bureau of Standards, Washington, D.C. 20234.
Summary
High-accuracy spectrophotometry of potassium dichromate solutions provides reliable absorbance measurements. These findings are crucial for calibrating spectrophotometers and ensuring accurate chemical analysis in various scientific fields.
Area of Science:
- Analytical Chemistry
- Spectroscopy
- Chemical Metrology
Background:
- Accurate absorbance measurements are fundamental for quantitative chemical analysis.
- Spectrophotometer calibration requires reliable standards and well-characterized absorbance values.
- Understanding Beer's Law deviations is essential for precise spectrophotometric determinations.
Purpose of the Study:
- To determine the absorbances of potassium dichromate solutions at specific ultraviolet wavelengths.
- To evaluate the suitability of these wavelengths for spectrophotometer calibration and accuracy checks.
- To assess the reproducibility and uncertainties in absorptivity values.
Main Methods:
- Measurements were performed using a high-accuracy spectrophotometer at the National Bureau of Standards.
- Absorbances of five potassium dichromate concentrations in perchloric acid were measured at eight UV wavelengths.
- Wavelengths corresponding to spectral maxima/minima and predicted isosbestic points were selected.
Main Results:
- Apparent absorptivities were reproducible to one part in a thousand.
- Estimated uncertainties in absorptivity were ±0.7% at 0.1 absorbance and ±0.2% near 1 absorbance.
- Wavelength 345 nm showed sufficient independence from concentration for linearity checks (0.2-1 A).
Conclusions:
- Specific ultraviolet wavelengths are suitable for checking the absorbance accuracy of narrow bandpass spectrophotometers.
- Potassium dichromate solutions, despite minor Beer's Law deviations, offer reliable standards for spectrophotometric calibration.
- The study provides precise absorptivity data crucial for metrological applications in analytical chemistry.
Keywords:
Absorbance linearityaccuracyacidic potassium dichromate solutionscalibration of ultraviolet spectrophotometersliquid filterstransfer standardsultraviolet absorbance standardsMore Related Videos
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