pro sat_equilib, p,t,qh2so4,vsat ;--------------------------------------------------------------------- ; ; Purpose: ; ; Routine computes the equilibrium volume of sulfuric acid ; tetrahydrate (SAT) ; ; Parameters: ; ; input: ; p........pressure, mb ; t........temperature, K ; qh2so4...total (condensed plus vapor) h2so4 mixing ratio, ppbv ; ; output: ; vsat.....SAT volume, um3/cm3 ; ; source: Mark Hervig ; ;--------------------------------------------------------------------- ;- some constants R = 8.314 ; J/mol/K Mw = 174.0 ; molec wt. SAT, g/mol Mws = 98.0 ; molec wt. h2so4 g/mol ds = 1.6 ; density of SAT, g/cm3 ws = 0.563 ; wt. fraction h2so4 in SAT ;- compute volume ns = (p*100.0) * (qh2so4*1.e-9) / (R*T) ; mols h2so4 per m3 air vsat = 1.0e6 * (ns * Mws) / (ws * ds) ; SAT volume, um3/cm3 return end