chromium complexes the reorganization energy is markedly larger and involves a much more important contribution of the vibration factoraZ2 It is thus conceivable that the harmonic approximation is less valid in the second case than in the first.On the other hand, it is noted that the value of a at E = E" + I& is smaller than predicted by the Marcus theory (0.5), the difference being more important in ACN than in DMF. A possible explanation of this phenomenon is that the solvation mode is different in the starting molecule and in the anion radical especially as far as preferential solvation by water is concerned. It is indeed likely that the primary interaction between the anion radical and water is the formation of a 1-1 adduct which would be involved in a Born-type solvation rather than the anion radical itself. In the framework of an harmonic approximation the parabola representing the potential energy of the product as a function of the reaction coordinate would then be more closed up than that corresponding to the reactant due to a strong close distance interaction between the negative charge and the water molecule in the 1-1 adduct. This would result in a standard value of cy (for 2197 "Electrochimie Organique").The solubility of mercury(I1) iodide in m-terphenyl and its vapor pressure in dilute solution in p-terphenyl were measured over a temperature range near its melting point. The results are compared with the expectation from solubility parameter theory, and it is concluded that the transfer of the mercury(I1) iodide from the liquid to its solution in either of the terphenyls, either directly or via the vapor, is considerably more endothermic than predicted from that theory, indicating self-interactions of the solvent which are disrupted in these processes.
The effect of pressure and hydrogen/oxygen ratio of a burning gas mixture on pulsed flame emission time‐dependence was investigated in the range of 0.1–5 atm using a specially designed pulsed flame photometric detector (PFPD). We studied the pressure and gas composition effect on the pulsed flame delayed light emission of sulfur, phosphorus, and nitrogen‐containing organic compounds. The optimal pressure conditions for nitrogen detection, intensity, and emission time delay was found to be 0.4 bar, at which the detection sensitivity could be improved by a factor of 2. For phosphorus, the optimal pressure obtained was 1.3 bar with 40% sensitivity improvement (compared with 1 bar). In the case of sulfur detection, two emission maxima were obtained, at 1.1 and 0.6 bar, at H/O ratio of 5. Increasing the H/O ratio resulted in the appearance of only one peak at 1 bar, and enhancement of the sensitivity by a factor of 2.4 at H/O ratio of 10.3. From the analytical point of view, we found that emission intensity is practically unchanged by the pressure and the H/O ratio for all three elements investigated in the range of 0.8–1.1 bar and H/O of 5–6. Thus, in addition to excellent sensitivity and improved selectivity, the PFPD can be applied under a variety of atmospheric pressure conditions in field environmental applications.
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