Heterogeneous chemistry of acetone in sulfuric, acid solutions: Implications for the upper troposphere

The uptake of acetone vapor by liquid sulfuric acid has been investigated o ver the range of 40-87 wt % H2SO4 and between the temperatures 198 and 300 K. Studies were performed with a flow-tube reactor, using a quadrupole mass spectrometer for detection. At most concentrations studied (40-75 wt %), a cetone was physically absorbed by sulfuric acid without undergoing irrevers ible reaction. However, at acid concentrations at or above 80 wt %, reactiv e uptake of acetone was observed, leading to products such as mesityl oxide and/or mesitylene, From time-dependent uptake data and liquid-phase diffus ion coefficients calculated from molecular viscosity, the effective Henry's law solubility constant (H*) was determined, The solubility of acetone in liquid sulfuric acid was found to increase with increasing acid concentrati on and decreasing temperature. In the 75 wt % and 230 K range, the value fo r H* was found to be similar to 2 x 10(6) M/atm. This value suggests that a cetone primarily remains in the gas phase:rather than absorbing into sulfat e aerosols under atmospheric conditions.