John Dalton

Another Presentation by Eisa Adil

Who was Dalton?

• John Dalton (6 September 1766 – 27 July 1844) was an English chemist.

• He provided the beginnings of the development of a scientific atomic theory, thus facilitating the development of chemistry as a separate science.

• His contributions to physics, particularly to meteorology, were also significant.

Who was Dalton?

• He is widely known for his research on Color Blindness, also called Daltonism, in his honor.

Early Life

• John Dalton (1766–1844) was born into a modest Quaker family in Cumberland, England, and earned his living for most of his life as a teacher and public lecturer.

• Until he was 11, he attended school, then at the age of 12 became a teacher.

• After teaching 10 years at a Quaker boarding school in Kendal, he moved on to a teaching position in the growing city of Manchester.

Early Life

• There he joined the Manchester Literary and Philosophical Society, which provided him with a stimulating intellectual environment and laboratory facilities.

• The first paper he delivered before the society was on color blindness, which afflicted him and is sometimes still called “Daltonism.”

Studies in Meteorology

• Dalton's lifelong interest in meteorology did much to make that study a science.

• He began keeping records of the local weather conditions, atmospheric pressure, temperature, wind, and humidity in 1787, and maintained them for 57 years until his death.

• During this time he recorded more than 200,000 values, using equipment which for the most part was made by him.

Studies in Meteorology

• Dalton's interest in the weather gave him a special interest in mixtures of gases, and his earliest studies were concerned with atmospheric physics.

• The formulation of his law of partial pressures (Dalton's law) was announced in 1803.

• It defined the pressure of a mixture of gases as the sum of the pressures exerted by each component solely occupying the same space.

Studies in Meteorology

• In 1800 he studied the heating and cooling of gases resulting from compression and expansion, and in 1801 he formulated a law of the thermal expansion of gases.

• His work on water vapor concentration in the atmosphere, using a homemade dew-point hygrometer, and his 1804 study of the effect of temperature on the pressure of a vapor brought him international fame.

The Atomic Theory• Less than twenty years earlier, in the 1780's, Lavoisier ushered in

a new chemical era by making careful quantitative measurements which allowed the compositions of compounds to be determined with accuracy.

• By 1799 enough data had been accumulated for Proust to establish the Law of Constant Composition ( also called the Law of Definite Proportions).

• In 1803 Dalton noted that oxygen and carbon combined to make two compounds. Of course, each had its own particular weight ratio of oxygen to carbon (1.33:1 and 2.66:1), but also, for the same amount of carbon, one had exactly twice as much oxygen as the other.

Antoine Lavoisier

The Atomic Theory

• This led him to propose the Law of Simple Multiple Proportions, which was later verified by the Swedish chemist Berzelius.

• In an attempt to explain how and why elements would combine with one another in fixed ratios and sometimes also in multiples of those ratios, Dalton formulated his atomic theory.

Antoine Lavoisier

Postulates of the Atomic Theory

All matter is composed of atomsAtoms cannot be made or destroyed

All atoms of the same element are identicalDifferent elements have different types of atoms

Chemical reactions occur when atoms are rearrangedCompounds are formed from atoms of the

constituent elements.

Dalton's theory was based on the premise that the atoms of different elements could be distinguished by differences in their weights. He stated his theory in a lecture to the Royal Institution in 1803. The

theory proposed a number of basic ideas:

Later Life• Dalton lived a simple life, kept to the doctrines of his Quaker

faith, and never married. • During most of his life he had little money and was almost

excessively economical; however, by tutoring and doing routine chemical work at low pay his few wants were met.

• He had no flair for lecturing: his voice was rather harsh, and he was inclined to be rather stiff and awkward in manner. He is said to have had no grace in conversation or in writing.

• Despite his lack of these social assets, he apparently lived a quite happy life and had many friends.

Later Life• In 1810 Dalton refused an invitation to join the Royal Society

but was finally elected in 1822 without his knowledge. • As his fame grew, he received many honors, including a

doctor's degree from Oxford in 1832, at which time he was presented to King William IV.

• For this occasion he had to wear the famous scarlet regalia of Oxford, which fortunately looked gray to his color-blind eyes and therefore was acceptable to him as an orthodox Quaker.

• In 1837 he suffered a damaging stroke; the following year another left him with impaired speech. A final stroke came on the night of July 26, 1844.