Burke R W, Mavrodineanu R
Institute for Materials Research, National Bureau of Standards, Washington, D.C. 20234.
J Res Natl Bur Stand A Phys Chem. 1976 Jul-Aug;80A(4):631-636. doi: 10.6028/jres.080A.062. Epub 1976 Aug 1.
The absorbances of five concentrations of potassium dichromate in 0.001 perchloric acid have been determined at eight wavelengths in the ultraviolet on the National Bureau of Standards Institute for Materials Research high-accuracy spectrophotometer. Four of the wavelengths-235, 257, 313, and 350 nm-correspond to absorbance maxima or minima in the HCrO spectrum and are useful wavelengths for checking the accuracy of the absorbance scale of narrow bandpass spectrophotometers. Although partial dimerization of HCrO to CrO produces small positive deviations from Beer's law at these wavelengths, the apparent absorptivities calculated for each concentration are reproducible to one part in a thousand. The estimated uncertainties in the absorptivity values are ± 0.7 percent at 0.1 absorbance () and ± 0.2 percent near = 1. These uncertainties include all known sources of possible systematic error and the 95 percent confidence level for the mean. The remaining four wavelengths used for measurement are near two predicted isosbestic points in the HCr0 /CrO spectra. The absorptivities at 345 nm are sufficiently independent of concentration that this wavelength can be used for checking absorbance linearity to one part in a thousand over the range = 0.2-1.
在美国国家标准局材料研究所高精度分光光度计上，测定了0.001 高氯酸中五种浓度重铬酸钾在紫外区八个波长处的吸光度。其中四个波长——235、257、313和350纳米——对应于HCrO 光谱中的吸光度最大值或最小值，是用于检验窄带通分光光度计吸光度刻度准确性的有用波长。尽管HCrO 部分二聚为CrO 在这些波长处会导致与比尔定律产生小的正偏差，但为每种浓度计算的表观吸光系数可精确到千分之一。吸光系数值的估计不确定度在吸光度为0.1时为±0.7%，在吸光度接近1时为±0.2%。这些不确定度包括所有已知的可能系统误差来源以及平均值的95%置信水平。用于测量的其余四个波长接近HCr0 /CrO 光谱中两个预测的等吸收点。345纳米处的吸光系数与浓度充分无关，以至于该波长可用于在吸光度范围为0.2 - 1时检验千分之一的吸光度线性。
