Chlorine is very active, so in nature it is found only in the form of compounds. The largest reserves of chlorine are contained in the composition of the salts of the waters of the seas and oceans (the content in seawater is 19 g / l). Chlorine accounts for 0.025% of the total number of atoms in the earth's crust.
The human body contains 0.25% chlorine ions by weight. In humans and animals, chlorine is found mainly in intercellular fluids (including blood) and plays an important role in the regulation of osmotic processes, as well as in processes associated with the work of nerve cells. The minimum human requirement for chlorine is about 800 mg per day. The infant receives the required amount of chlorine through the mother's milk, which contains 11 mmol / L of chlorine. The table salt we add to our food is nothing more than sodium chloride. NaCl is essential for the production of hydrochloric acid in the stomach, which aids digestion and kills bacteria.
Pure chlorine was first obtained in 1774 by the Swedish chemist Karl Scheel. Currently, it is obtained in a cheap way, passing an electric current through a solution of sodium chloride.
Chlorine is a toxic asphyxiant gas that, when it enters the lungs, causes burns of the lung tissue, asphyxiation. It was one of the first chemical warfare agents used by Germany in the First World War. However, in World War II, despite the fact that both opposing sides possessed large reserves of poisonous gases, it was not used in hostilities.
Part of many herbicides and disinfectants, chlorine kills germs. In many cities, water treatment systems use chlorine to kill bacteria. In this case, four to five parts of chlorine are used for one million parts of water. This amount is harmless to humans, but sometimes the water tastes like chlorine.
Chlorine can be converted to liquid through refrigeration and high pressure. Liquid chlorine is transported in metal containers or special tanks.
Chlorine is used in bleaching and in the manufacture of bleaching powders. Chlorine is especially widely used in paper bleaching. It is also used in dyes, and compounds with oxygen and potassium in the creation of fireworks, as well as in the manufacture of matches.
In terms of electrical conductivity, liquid chlorine ranks among the strongest insulators: it conducts current almost a billion times worse than distilled water, and 10 to 22 times worse than silver. The speed of sound in chlorine is about one and a half times less than in air.