The need for a means of testing the reliability of the photometric scale of spectrophotometers in the ultraviolet region (where glasses are unsuitable) has led to the study of an aqueous solution of potassium chromate having the following composition: 0.0400 gram per liter of K2CrO4 in 0.05 N KOH. Based on extensive measurements using photographic, photoelectric, and visual spectrophotometry, standard values of spectral transmittancy have been determined for 1.000 and 2.000 cm of solution at 25°C from 220 to 500 mμ. These values have been tabulated along with derived values of absorbancy, molar absorbancy index aM, and log10aM. The latter values have been compared graphically with those of other observers. Changes in spectral transmittancy with changes in temperature have been determined. The investigation has also included a study of the effects due to the container bottle and to age of solutions over periods up to eight years, and a comparison of results obtained with the solution prepared either from K2CrO4 or from K2Cr2O7 as one of the reagents.
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