Air & Water Quality Glossary Precipitate As a verb: to cause a dissolved substance to form a solid which comes out of solution and can be removed by settling or filtering. For example, the removal of dissolved iron by oxidation, precipitation and filtration. As a noun: the solid formed when a dissolved substance comes out of solution in such a way that it can be settled or filtered out. Previous Page Home | Top of page | Contact © Copyright 2000, Air & Water Quality, Inc. Maine's Water Experts