Life of John Dalton

John Dalton

John Dalton, born 6th September 1766, is known for developing the theory of the elements and compounds atomic mass and weights and his research in colour blindness.

He was born in Eaglesfield, Cumberland (now know as Cumbria). In school he was so successful that at the age of 12 he became a Teacher. In 1785 he became one of the principles and in 1787 he made a journal that was later made into a book, describing his thoughts on mixtures of gases and how each gas acted independently and the mixtures pressure (which is the same as the gases volume if it had one). Therefore the law of partial pressures was made. It is said that in 1790, Dalton?s aims were to pick up in law or medicine, but he got no encouragement from his family. In 1793 he moved to Manchester where he was appointed Professor of Mathematics and Natural Philosophy at a Dissenting New College. He stayed there until 1799 when he made his own academy.

In 1794 he was elected a member of the Manchester Literary and Philosophical Society. There he read his papers and identified the phenomenon of colour blindness, which he and his brother shared. When showed a colour spectrum besides blue and purple Dalton was only able to recognise one other colour, yellow. Or as he says ?that part of the image which others call red appears to me little more than a shade or deflect of light. After that the orange, yellow and green seem one colour which descends pretty uniformly from an intense to a rare yellow, making what I should call different shades of yellow?

In 1801 he argued that the atmosphere was filled with mechanical gases and that the chemical reactions between the nitrogen and oxygen played no part in the atmosphere?s construction. To prove this he conducted a lot of experiments on the solubility of gases in water. This showed that dissolved gases were mechanically mixed with the water and weren?t mixed naturally. But in 1803 it was found that this depended on the weight of the individual particles of the gas or atoms. By assuming the particles were the same size Dalton was able to develop the idea of atomic weights.

In 1803 this theory was finalised and stated that (1) all matter is made up of the smallest possible particles termed atoms, (2) atoms of a given element have unique characteristics and weight, and (3) three types of atoms exist: simple (elements), compound (simple molecules), and complex (complex molecules).