Dalton's law

Etymology
From John Dalton, English scientist.

Proper noun

 * 1)  The total pressure of a mixture or gases is the sum of the partial pressures of each gas in the mixture; it is only true for ideal gases.
 * 2)  When two elements can combine to form more than one compound then the amounts of one which combines with a fixed amount of the other will have a simple multiple relationship.

Synonyms

 * the law of partial pressures (1)
 * the law of multiple proportions (2)