Abstract
This report describes the theory and experimental measurements related to the ability of both the current ACGIH recommended method and an alternative approach called VAPRAT to predict the ratios of vapors evaporating from multicomponent solvent mixtures. The current ACGIH “approximate solution” does not account for nonideal effects common in many organic solvent mixtures nor for differences in the relative volatilities of individual components. It was concluded that errors ranging between 10 and 1000% using the ACGIH method are unacceptable for many occupational health programs. Laboratory tests with VAPRAT (an acronym for VAPor RATios) resulted in maximum errors of 20%. VAPRAT promises to be a useful alternative in the future for such applications as predicting the solvent mixture concentration from the measurement of a single component, adjusting TLVs for the presence of these other vapors, or for predicting the effects of solvent substitution.