Dalton’s Law

In 1801, English scientist John Dalton realized that each gas in a mixture of gases exerts a pressure, called a partial pressure.

John Dalton (1766-1844), an English schoolteacher, made a number of important contributions to chemistry. He was the first to notice the independent behavior of gases in mixtures.

In 1803, he published a summary statement concerning this behavior that is now known as Dalton’s law of partial pressure, although the French chemist and physicist Joseph Gay-Lussac claimed that the ‘Law’ had previously been described during the French Revolution attributed it to Citizen Charles.

Dalton’s law of partial pressure states that the total pressure exerted by a mixture of gases is the sum of the partial pressures of the individual gases present.
Dalton’s Law

Raoult’s Law

Raoult’s Law is named for François-Marie Raoult (10 May 1830 – 1 April 1901) a French chemist who was one of the founders of physical chemistry.  He gave an important law about vapor pressure of the solution, known as Raoult’s law.

He observed experimentally that - in liquid-vapor phase equilibrium of a mixture - the partial pressure of a vapor constituent is proportional to the mole fraction of that constituent in the solution.

Raoult also investigated freezing point depression of solvents when a small amount of solute is introduced. In 1882, Raoult published his results on the effects of nondissociating organic solutes, from which he deduced a general law controlling the lowering of freezing points. Four years later he extended this work to show the effect of solutes on a vapor pressure.

Raoult’s Law is strictly applicable to ideal liquid solutions at all compositions, pressures and temperatures. In an ideal of perfect solution, the components are mutually miscible in all proportions and there are no volume or thermal changes on mixing.

Raoult published the formulations of his laws in the Comptes rendus for 1882 and 1887.
Raoult’s Law

Planck's law of black-body radiation

In 1893, German physicist Wilhelm Carl Wien advanced the black body research by developing relationship between the wavelength of peak emission of radiant energy by a black body and its absolute temperature (T).

A black body is a system that absorbs all the radiation that falls on it. For instance, a matte black body surface or a large cavity with a small hole in its wall is a black body and emits black body radiation.

In 1859, G.R Kirchhoff verified that the ratio so the emissive power to the absorptivity at a given temperature T is the same for all bodies, irrespective of the material of which the body is made.

In 1900, Lord Rayleigh proposed a new black body radiation law which was later modified by J. Jeans in 1905 and is now known as the Rayleigh-Jeans formula.

In his investigation, to find a relation between the radiation emitted by a black body as a function of temperature and wavelength, Max Planck (1858-1947) developed the now famous equation named after him.

He reported his findings, which were based on his experimental work on October 19, 1900. Planck's law describes the electromagnetic radiation emitted by a black body in thermal equilibrium at a definite temperature. It describes the distribution of energy radiated by a black body. It is a pioneering result of modern physics and quantum theory.

His efforts laid the foundation of the quantum theory, for which he received the Nobel Prize in 1918.
Planck's law of black-body radiation

Archimedes of Syracuse

Archimedes of Syracuse
He was Greek engineer who made the first measurement of specific gravity.

He studied in Alexandria, after which he returned to Syracuse where he spent most of the rest of the life.

He made many mathematical discoveries, including the most accurate calculation of pi made up to that time.

In engineering he was the founder of the science of hydrostatics. He is well known for the discovery of ‘Archimedes Law’ that a body wholly or partly immersed in a fluid loses weight equal to the weight of the fluid displaced.

He thus made the first measurement of specific gravity.

Archimedes also proved the law of the lever and developed the theory of mechanical advantage boasting to his cousin Hieron, ‘Give me a place to stand on and with a lever I will move the whole world.’

To prove his point, he launched one of the biggest ships built up to that date.
During his time in Egypt he devised the ‘Archimedean Screw’, still used today in Middle Eastern countries for pumping water.

He also built an astronomical instrument to demonstrate the movements of the heavenly bodies, a form of orrery.

He was General of Ordnance to Heiron and when the Romans besieged Syracuse, a legionary came across Archimedes geometrical diagrams in he sand.

Archimedes immediately told him to ‘Keep off’ and the soldier killed him.

He also experimented with burning glasses and mirrors or setting for to wooden ships.
Archimedes of Syracuse