Joanne Ruggiero, age 14, of Pittsburgh, Pa., for his question:

WHO WAS JOHN DALTON?

John Dalton was an English chemist who formulated the law of partial pressures in gases in 1802. The law says that for an ideal gas, the total pressure of a confined gas mixture equals the sum of the pressure each gas would exert alone in the same volume.

Dalton proposed an atomic theory of matter in 1803 that became one of the foundations of chemistry.

Long ahead of other men in his field, Dalton was the first to determine chemical formulas that showed the atomic composition of molecules.

John Dalton was also the first to make a table of atomic weights, although his findings were later found to be inaccurate. He also investigated color blindness, called Daltonism, which he had.