Henry's law constant determinations for hydrogen peroxide, methyl hydroperoxide, hydroxymethyl hydroperoxide, ethyl hydroperoxide, and peroxyacetic acid

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The temperature-dependent solubilities of hydrogen peroxide (H2O2), hydroxymethyl hydroperoxide (HOCH2O2H), methyl hydroperoxide (CH3O2H), peroxyacetic acid (CH3C(O)O2H), and ethyl hydroperoxide (C2H5O2H) were determined under conditions used in the aqueous collection and analysis of atmospheric hydroperoxides. Henry's law was obeyed over the source concentration range employed, nominally 10-6-10-2 M. Measurements were made using either pH = 3 or pH = 6 source and collection solutions. The temperatures investigated ranged from 4 to 28°C. A solution pH 3 was used for experiments with H2O2, HOCH2O2H, and CH3C(O)O2H since these compounds decompose in less acidic solution. The solubility of HOC2H4O2H could not be accurately determined because of its rapid decomposition in solutions with pH > 3. The Henry's law solubility of H2O2, HOCH2O2H, CH3O2H, and CH3C(O)O2H are in agreement with prior determinations. The solubility measurement of C2H5O2H is the first of its kind. Dimensional Henry's law constants (M/atm) can be expressed by ln(Kh) = A/T - B, where T is in degrees kelvin. Kh at 25°C and the A and B coefficients are compound A B Kh (M atm-1) H2O2 7379 ± 156 13.42 ± 0.54 8.33 × 104 ± 3.8 × 103 CH3O2H 5241 ± 133 11.84 ± 0.46 311 ± 14 HOCH2O2H 9652 ± 53 18.04 ± 0.18 1.67 × 106 ± 3.5 × 105 CH3C(O)O2H 5308 ± 672 11.07 ± 2.34 837 ± 175 C2H5O2H 5995 ± 200 14.28 ± 0.70 336 ± 20 The high solubility of HOCH2O2H implies it will be efficiently removed from the atmosphere by precipitation or surface deposition. Its decomposition and that of HOC2H4O2H and CH3C(O)O2H forming H2O2 near neutral pH suggest these hydroperoxides may constitute a heterogeneous source of H2O2 in atmospheric water if they are formed in the troposphere. The solubility of the listed organic hydroperoxides and the propensity of three of them to decompose at neutral pH further underscores the potential for interference's and artifacts in the aqueous collection and nonspecific analysis of H2O2 in the atmosphere. © 1996 American Chemical Society.

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Journal of Physical Chemistry