How did John Dalton explain the behavior of gases in a mixture?

John Dalton explained the behavior of gases in a mixture through his concept of partial pressure, which states that the total pressure of a gas mixture is equal to the sum of the pressures that each individual gas would exert if it occupied the volume of the mixture alone at the same temperature.12

To account for this behavior, Dalton proposed that in a mixture of gases, only like atoms repel one another, while unlike atoms react indifferently toward each other. This conceptualization allowed him to conclude that each gas in a mixture behaves independently. Although this specific explanation regarding atomic repulsion was later shown to be erroneous, it served as a foundational step in his development of atomic theory, helping him move away from the idea that all atoms of matter are identical.2