Law of Multiple Proportions Definition - Chemistry Glossary

by Anne Marie Helmenstine, Ph.D.
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
Updated March 06, 2017

Law of Multiple Proportions Definition: Law which states that when elements combine, they do so in the ratio of small whole numbers (assuming they have the same type of chemical bonds).

Also Known As: Dalton's Law, though that term usually refers to his law of partial pressure

Examples: carbon and oxygen react to form CO or CO2, but not CO1.6