The parameterization scheme for sulfate washout derived by Scott <1978> is modified to allow estimation of the relative contributions of nucleation scavenging, in-solution production, and below-cloud scavenging to the sulfate content of precipitation. The parameterization scheme predicts changes in precipitation sulfate concentration by up to a factor of 6 for large variations in key cloud physics parameters. The results suggest in-solution sulfate production can be substantial contributor to the sulfate content of precipitation.