(September 6, 1766 – July 27, 1844)
Celebrated for his atomic theory, which ushered-in particle physics and nuclear chemistry, Dalton was among the most influential chemists of the 19th century. He debuted as a meteorologist: a profession he learned by assisting Elihu Robinson in both weather forecasting and instrument manufacturing. Although his treatise titled Meteorological Observations and Essays barely circulated, he kept faith in his studies: using what he observed to maintain weather records for nearly 60 years. Dalton also worked for a while as a math tutor. It was while on this job at New College (in Manchester) that he researched on deuteranopia (a red-green type of colorblindness which ran in his family and afflicted him and his older brother, Jonathan). His treatise, titled Extraordinary Facts relating to the Vision of Colours, with Observation, was the first scientific journal to address this genetic defect. As a result of his pioneering research, this type of colorblindness is called Daltonism. Having been fascinated by the components and behavior of matter, he experimented with gases at variable temperatures and pressures. His inferences led him to what became known as Dalton’s Law of Partial Pressures. Further experiments helped him come-up with the Law of Multiple Proportion. His experiences convinced him that chemical reactions entail the unions of microscopic particles, which he called atoms. His atomic theory that helped lay the foundations of modern chemistry was thus entrenched. Although his postulations were themselves modified, their underlying insights remained inspiring. The 60-kilometer-wide Dalton lunar crater (bordering Einstein) is named after him.