Solubilities of the halides, nitrates, carbonates, sulfates, and some
perchlorates of all the alkali metals
and alkaline earth metals in methanol at room temperature have been
determined. Data on some, such
as cesium and rubidium fluoride, nitrate, carbonate, and sulfate,
appear to be reported for the first time.
Comparison with earlier results from the literature reveals a
number of discrepancies.
estimating the intersection point and the positioning of the sample cell in the Dewar flask. It should be noted that the correction factors for tryptophan and tyrosine are 1.00 because the molar absorptivities are quite small at the wavelengths being used and the solutions are dilute.The measured intensity ratio of the two components of a mixture is a function of the wavelength of excitation, of the wavelength at which emission is measured, and of the sensitivity of measurement of the individual components. This assumes that the decay times of the two components are sufficiently different that an analytically useful logarithmic decay curve results. Note that the mixture of tryptophan-tyrosine is easily resolvable even though the ratio of decay times is only 4.6. The concentration ratio of the components in a two-component mixture can vary considerably if the analyst is willing to sacrifice sensitivity and accuracy of measurement of one or both of the components.Several other uses of the measurement system should be mentioned. Phosphorescence decay times greater than 0.2 second can be simply measured by measuring the slope of the logarithmic decay curve for the component in concern.It is also simple to check the purity of any phosphorescent molecule by verifying the linearity of the logarithmic decay curve. It should, however, be pointed out that non-exponential decays have been observed for some pure organic phosphors (8-10). For example, the authors have failed to obtain exponential decays for high purity benzyl alcohol and toluene in absolute ethanol.
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