3. John Dalton (6 September 1766 – 27 July 1844) was an English chemist, meteorologist and physicist. He is best known for his pioneering work in the development of modern atomic theory, and his research into colour blindness (sometimes referred to as Daltonism, in his honour).

5. Atomic theory In 1800, Dalton became a secretary of the Manchester Literary and Philosophical Society, and in the following year he orally presented an important series of papers, entitled "Experimental Essays" on the constitution of mixed gases; on the pressure of steam and other vapours at different temperatures, both in a vacuum and in air; on evaporation; and on the thermal expansion of gases. These four essays were published in the Memoirs of the Lit & Phil in 1802.vapours The second of these essays opens with the striking remark, There can scarcely be a doubt entertained respecting the reducibility of all elastic fluids of whatever kind, into liquids; and we ought not to despair of affecting it in low temperatures and by strong pressures exerted upon the unmixed gases further. After describing experiments to ascertain the pressure of steam at various points between 0 and 100 °C (32 and 212 °F), Dalton concluded from observations on the vapour pressure of six different liquids, that the variation of vapour pressure for all liquids is equivalent, for the same variation of temperature, reckoning from vapour of any given pressure. In the fourth essay he remarks, I see no sufficient reason why we may not conclude that all elastic fluids under the same pressure expand equally by heat and that for any given expansion of mercury, the corresponding expansion of air is proportionally something less, the higher the temperature. It seems, therefore, that general laws respecting the absolute quantity and the nature of heat are more likely to be derived from elastic fluids than from other substances

6. Five main points of Dalton's atomic theory 1.The atoms of a given element are different from those of any other element; the atoms of different elements can be distinguished from one another by their respective relative atomic weights. 2.All atoms of a given element are identical. 3.Atoms of one element can combine with atoms of other elements to form chemical compounds; a given compound always has the same relative numbers of types of atoms. 4.Atoms cannot be created, divided into smaller particles, nor destroyed in the chemical process; a chemical reaction simply changes the way atoms are grouped together. 5.Elements are made of tiny particles called atoms.

7. Various atoms and molecules as depicted in John Dalton's A New System of Chemical Philosophy

8. In Dalton’s atomic model, an atom is a solid sphere, similar to a billiard ball. This simple model is still used today to represent the arrangement of atoms in molecules. Billiard Ball Model

9. In 1794, shortly after his arrival in Manchester, Dalton was elected a member of the Manchester Literary and Philosophical Society, the "Lit & Phil", and a few weeks later he communicated his first paper on "Extraordinary facts relating to the vision of colours", in which he postulated that shortage in colour perception was caused by discolouration of the liquid medium of the eyeball. In fact, a shortage of colour perception in some people had not even been formally described or officially noticed until Dalton wrote about his own. Although Dalton's theory lost credence in his own lifetime, the thorough and methodical nature of his research into his own visual problem was so broadly recognized that Daltonism became a common term for color blindness. Examination of his preserved eyeball in 1995 demonstrated that Dalton actually had a less common kind of colour blindness, deuteroanopia, in which medium wavelength sensitive cones are missing (rather than functioning with a mutated form of their pigment, as in the most common type of colour blindness, deuteroanomaly). Besides the blue and purple of the spectrum he was able to recognize only one colour, yellow, or, as he says in his paper, coloursdeuteroanopia deuteroanomalybluepurplespectrumyellow that part of the image which others call red appears to me little more than a shade or defect 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 yellowredlightorangegreen This paper was followed by many others on diverse topics on rain and dew and the origin of springs, on heat, the colour of the sky, steam, the auxiliary verbs and participles of the English language and the reflection and refraction of light.raindewspringsheatskysteamauxiliary verbs participlesEnglish languagereflectionrefraction Colour blindness