azeotropic solvents. Cosolvent systems are flexible in that different proportions of substances in the zeotropic mixture can be used to satisfy different cleaning purposes. For example, increasing the proportion of solvating agent to rinsing agent in the mixture increases the solvency, and thus is used for removing heavier soils. The operating temperature of the system depends on the boiling point of the mixture, which in turn depends on the compositions of these agents in zeotropic mixture. Since zeotropic mixtures have different boiling points, the cleaning and rinse sump have different ratios of cleaning and solvating agents. The lower-boiling point solvating agent is not found in the rinse sump due to the large difference in boiling points between the agents. Examples of zeotropic solvents Mixtures containing HFC-43-10mee can replace CFC-113 and perfluorocarbon (PFC) as solvents in cleaning systems because HFC-43-10mee does not harm the ozone layer, unlike CFC-113 and PFC. Various mixtures of HFC-43-10mee are commercially available for a variety of cleaning purposes. Examples of zeotropic solvents in cleaning processes include: Zeotropic mixtures of HFC-43-10mee and hexamethyldisiloxane can dissolve silicones and are highly compatible with polycarbonates and polyurethane. They can be used to remove silicone lubricant from medical devices. Zeotropic mixtures of HFC-43-10mee and isopropanol can remove ions and water from materials without porous surfaces. This zeotropic mixture helps with absorption drying. Zeotropic mixtures of HFC-43-10mee, fluorosurfactant, and antistatic additives are energy-effiicient and environmentally safe drying fluids that provide spot-free drying. See also List of Refrigerants Azeotrope References Chemical engineering thermodynamics