Dalton,John (1766-1844)

was a highly original English scientist who studied a wide range of topics in science. Dalton is best known, however, for his contributions to the atomic theory in of matter. The atomic theory proposes that all matter is made up of very tiny particles called atoms. Dalton refined the theory by suggesting that each chemical element consists of a Single type of atom. Although an amount of the element may contain many, many atoms, they are all identical in size, shape, and mass. Further-more, Dalton theorized that in a chemical compound, the atoms of the different elements always combine in the same ratio.
In a similar vein, Dalton arranged all of the known chemical elements in a table according to atomic weight (Dalton understood that each element has a unique atomic weight, since the atoms of each element are unique.) Dalton's table was a very early version of the periodic table developed in the later 1800's by Dmitri Mendeleev and others. Dalton also devised a system of chemical symbols to use in formulas. Dalton made fundamental contributions to the scientific understanding of gases. He first stated the law of partial pressures. This law e plains that the total pressure in a mixture of gases equals the sum of the pressure exerted independently by each gas. It is now called Dalton's law. Another chemical law credited to Dalton states that a gas expands as it is heated (This law is now called Charles' law -even though Dalton really discovered it first) And, Dalton proved that gases dissolve in water. H also proved the rate of diffusion of gases. Early in life, Dalton developed a strong interest in meteorology, the scientific study of weather. He was one of the first people to study weather from a scientific viewpoint. Dalton confirmed that rain falls when the temperature of a cloud declines, not because of a drop in atmospheric pressure. He also developed a theory to explain the cause of the trade winds, which occur in the latitudes of the earth near the equator. Dalton said that the trade winds were caused by a combination 0 the earth's rotation and temperature variation in the earth's atmosphere. Dalton studied the aurora borealis an occasional brilliant, shimmering display of lights in the northern skies He concluded that the earth's magnetism was at least part of the cause of the aurora. Later scientific findings proved Dalton largely correct in these theories. Dalton also investigated the condition known as color blindness. John and his brother had this condition, in which a person fails to perceive colors accurately. Because ol Dalton's work, the condition of color blindness. is also known as Daltonism. A member of the Royal Society, DaIton received a Gold Medal in 1826. He was also a corresponding member of the French Academy of Sciences and a founding member of the British Association for the Advancement Science. John Dalton died in 1844.