In Avogadro hypothesized that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules. From this hypothesis it followed that relative molecular weights of any two gases are the same as the ratio of the densities of the two gases under the same conditions of temperature and pressure. Avogadro also astutely reasoned that simple gases were not formed of solitary atoms but were instead compound molecules of two or more atoms. Thus Avogadro was able to overcome the difficulty that Dalton and others had encountered when Gay-Lussac reported that above o C the volume of water vapor was twice the volume of the oxygen used to form it. According to Avogadro, the molecule of oxygen had split into two atoms in the course of forming water vapor.
Lavoisier's successes stimulated chemists to search out and explore other areas in which accurate measurements might illuminate the study of chemical reactions. The acids comprised one such area. Acids form a natural group sharing a number of properties. They tend to be chemically active, reacting with metals such as zinc, tin, or iron, dissolving them and producing hydrogen. They taste sour if dilute enough or weak enough to be tasted with impunity , cause certain dyes to change colors in certain ways, and so on. Opposed to the acids is another group of substances called bases.
He is best known for introducing the atomic theory into chemistry, and for his research into colour blindness , sometimes referred to as Daltonism in his honour. Dalton was the first scientist to use the term atom for the smallest particle of matter, which originated from Greek word 'atomos' meaning cannot be divided further. Dalton's family was too poor to support him for long and he began to earn his living, from the age of ten, in the service of wealthy local Quaker Elihu Robinson.
He was the eldest of five children of Antoine Gay, lawyer and procureur royal at St. His father, to distinguish himself from others with the surname Gay in the Limoges region, had begun to call himself Gay-Lussac after the family property near St. The comfortable social and economic position of the family was rudely disturbed by the Revolution.