British scientist john dalton (1766 ~ 1844) introduced the atomic hypothesis into the mainstream of science at the beginning of19th century. The key theory he provided has made great progress in the field of chemistry since then. By the way, Dalton is color blind. The symptoms of the disease aroused his curiosity. He began to study this topic and finally published a paper on color blindness-the first paper on color blindness in history. As a person suffering from color blindness, Dalton can make such great achievements that future generations can feel the great glory of a scientific giant.

Dalton studied hard all his life and made scientific experiments seriously, and made simple instruments such as barometer and thermometer to analyze air samples collected from villages, cities, mountains and deep valleys. Although he is not an analytical chemist, he draws a conclusion from his own experimental results: all the air components from different places are the same. He asked himself: After water and oil are mixed, the oil is lighter and floats on the upper layer, while the water is heavier and sinks below. And why can different light and heavy gases in the air be evenly mixed? He thinks this is because air keeps flowing from one place to another. From this, he thought of the atomism of material composition in ancient natural philosophy. After his constant experimental exploration, 1803 put forward atomism: ① The final composition of elements is called simple atoms, which are invisible, can neither be created nor destroyed, nor can they be separated. (2) The atomic shape, mass and various properties of the same element are the same, but the atomic shape, mass and various properties of different elements are different. Each element is characterized by its atomic mass. (3) The atoms of different elements combine in a simple number ratio to form a chemical combination phenomenon. The atoms of a compound are called compound atoms. The mass of a complex atom is the sum of the atomic masses of various elements. Compound atoms of the same compound must have the same shape, mass and properties. Although Dalton's view of atomism has many shortcomings, it is it that brings chemistry into a new era.