A re-examination of the photoionization of HCN has revealed two processes, HCN + hν→H + +CN−, and HCN + hν→H + +CN+e, not previously reported. The difference in threshold values for the two processes leads directly to the electron affinity for CN, 3.82 ± 0.02 eV. The threshold for the second process leads to ΔHf0°(CN) = 105.5 ± 2 kcal/mole, but ΔHf°(HCN) remains a major source of uncertainty.

Photoionization-efficiency curves for CFa+ from CF 4 and for the parent ion and selected fragment ions from C2F4 are reported for the energy region from onset of ionization to about 20 eV. The ionization-efficiency curves for both parent and fragment ions from C2F4 demonstrate a number of very pronounced autoionization peaks. Appearance potentials are made more reliable by using a cooled ionization chamber to remove most of the thermal vibrational energy of the molecules. From the difference between the appearance potentials of CF+ and CFa+ from C2F 4 , it is concluded that J.P. (CF) =J.P. (CFa) +0.06 eV. Therefore the J.P. (CF) =9.23±0.08 eV can be calculated from the J.P. (CFa) =9.17±0.08 eV derived in this paper. The onset of CFa from CF4 is asymptotic, and there is no clear threshold. An upper limit for this threshold was set at 15.35 eV.

1 A reactivity scale for organic compounds based on ozone production is developed. It is based on the concept that ozone can be considered as the intermediate ( B ) of two consecutive reactions, A -B -C. The organic compound, A, is assumed to react only with OH radicals that are present in the atmosphere. It is also assumed that the organic compound is completely oxidized to either COz and/or formic acid. A reactivity scale based on these premises heavily weighs the number of carbon and hydrogen atoms present in the compound. The scale, developed only on theoretical grounds, predicts that all hydrocarbons lead to ozone formation and that the larger molecules lead to larger quantities of ozone. The reactivity scale predicts that high concentrations of ozone would be expected in rural downwind areas away from high emissions sources. This is in agreement with recent findings of high ozone levels in rural areas.Organic matter including hydrocarbons is essential for the formation of photochemical smog. However, not all hydrocarbons manifest themselves equally in the smog symptoms such as eye irritation, plant damage, visibility reduction, and oxidant formation. The literature suggests that several of these symptoms of reactivity must be considered when planning control strategies (1-3). However, for the present, oxidant/ozone is the only photochemical product for which there is an Air Quality Standard. Achievement of the oxidant standard is based on control of organic emissions.The role of the oxidant precursors, Le., the hydrocarbons, has been extensively studied in many laboratories over the past several years. Various parameters such as types of hydrocarbons, HC/NO, ratios, light intensity, water vapor, and temperature have all been investigated for possible effects on oxidant formation (1). From these studies, definitions of reactive organics such as those given in Rule 66 ( 4 ) have been developed by the Los Angeles County. The Rule 66 approach is to limit the emissions of hydrocarbons that are relatively high in reactivity with the expectation that this will result in a decrease in the amount of oxidant produced in the atmosphere of Los Angeles County.Appendix B in the Federal Register (August 1971) tends to overlook the relative reactivities of different hydrocarbons and puts forth the concept that all but a few hydrocarbons should be controlled. This approach severely limits emissions of all but the most unreactive hydrocarbons.More recently, a linear summation model for the control of hydrocarbons has been proposed ( 5 ) . With this model, hydrocarbons are classified according to five reactivity classes. Any combination of these five classes could be emitted into the atmosphere as long as the linear summation does not exceed the reactivity of the class of least reactive hydrocarbons.Some recent findings in the Midwest by EPA (6), as well as recent investigations ( 7 , 8 ) of high oxidant in rural areas, have led us to look into the formation of high oxidant concentrations from the so-called unreactive hydroca...

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Ozonation, on the other hand, did not result in the formation of any of these volatile halogenated compounds. The concentration of these compounds actually decreased during ozonation, possibly resulting from both stripping and oxidation of these compounds by the ozone.Therefore, with the ozonation process, organic compounds can ultimately be converted to harmless carbon dioxide by intensive ozonation of water. Cost, however, appears to be the major obstacle to the wide application of ozonation. Effective coagulation and sedimentation in the early stages of water treatment would tend to decrease ozone demand; incorporating UV irradiation and catalysts would enhance organic removal. These approaches would lower the ozonation cost.Further cost reductions can be realized through the development of efficient ozone generators and contactors and by obtaining knowledge about optimal conditions for ozonation reactions including such factors as reactor design, pH adjustment, temperature control, and application of UV. Future studies should therefore be directed toward minimizing costs by optimizing ozonation processes and toward assessing the health hazards associated with ozonation. ConclusionsUpon ozonation, 2-propanol was converted to acetone that