The scientific field has witnessed the emergence of many great physicists and chemists, but it is incomplete without the mention of the great British chemist, meteorologist and physicist John Dalton. His tremendous efforts led to the evolution of modern atomic theory. He was the first person to record colour blindness. He also carried out his research to explain the shortage of colour perception.
Dalton was born into a modest Quaker family in Cumberland, England around 5th September 1766. He got his early education from his father and his teacher, John Fletcher of the Quakers’ school at Eaglesfield, on whose retirement in 1778 he himself began teaching. He spent most of his life teaching and giving public lectures. After serving ten years at a Quaker boarding school in Kendal, in 1793 he took another teaching position in the rapidly increasing city of Manchester. There, he taught maths and natural philosophy at the “New College” until 1800, when he resigned due to worsening financial condition of the college. Afterwards, he gave private tuitions for mathematics and natural philosophy.
Most of the credit of Dalton’s interests in mathematics and meteorology goes to Elihu Robinson, an experienced meteorologist and instrument maker who greatly influenced his initial years of life. At Kendal, Dalton proposed the solutions of problems and questions on various subjects to the Gentlemen’s and Ladies’ Diaries, and starting in 1787 he maintained a meteorological diary in which during the succeeding fifty-seven years he entered over 200,000 observations.
His first separate publication was Meteorological Observations and Essays (1793), which explained many of his later discoveries; but in spite of the originality of its content, the book met with only a limited attention. Another work by him was published in 1801 as Elements of English Grammar.
In 1794, John joined the Manchester Literary and Philosophical Society, which provided him with an exciting academic environment and laboratory services. After a few weeks he presented his first paper on “Extraordinary facts relating to the vision of colours” before the society. In this paper he explained that the shortage in colour perception was caused by the discolouration of the liquid medium of the eyeball. He himself was a victim of colour blindness and was the first one to discover the concept. As a result ‘Daltonism’ became synonymous with colour blindness.
Dalton’s greatest interest was in meteorology and he maintained the daily records of local temperature, wind, humidity and atmospheric pressure using instruments that he devised himself. By 1800, he was appointed the secretary of the Manchester Literary and Philosophical Society and published a series of papers entitled “Experimental Essays on the constitution of mixed gases; on the force of steam or vapour of water and other liquids in different temperatures, both in Torricellian vacuum and in air; on evaporation; and on the expansion of gases by heat”.
In 1803, he published his gas law which is now known as ‘Dalton’s law’. In this law he basically stated that the total pressure exerted by a gaseous mixture is equal to the sum of the partial pressures of each individual component in a gas mixture.
He calculated the atomic weights of elements and assembled them in a table which consisted of six elements, namely hydrogen, oxygen, nitrogen, carbon, sulphur and phosphorus. He calculated these weights from percentage compositions of compounds using an arbitrary system to determine the probable atomic structure of each compound.
John Dalton’s Atomic theory has three principles that remain relatively unchanged. First, elements are made of the smallest particles called atoms. Second, all atoms for a particular element are identical. Third, atoms of different elements can be told apart by their atomic weight. Fourth, atoms of different elements can combine in a chemical reaction to form chemical compounds in fixed ratios. Finally, atoms cannot be created, destroyed or divided as they are the smallest particles of matter. Even though some of its postulates were opposed by many scholars and scientists yet Dalton’s Atomic Theory stills holds a lot of significance as it created a basis for current science.
Dalton died of a stroke on 27 July, 1844 and was buried in Manchester in Ardwick cemetery.
