Chlorine is a poisonous gas.
It mainly invades the human body through the respiratory tract and dissolves in the moisture contained in the mucosa, producing hypochlorous acid and hydrochloric acid, which have harmful effects on the upper respiratory mucosa: hypochlorous acid makes the tissue strongly oxidized; Hydrochloric acid stimulates inflammatory swelling of mucous membrane, which causes edema of respiratory mucosa and a large amount of mucus secretion, resulting in dyspnea, so the obvious symptom of chlorine poisoning is severe cough.
when the symptoms are severe, pulmonary edema will occur, which will make the circulation difficult and lead to death. Chlorine gas entering the human body from the esophagus can cause nausea, vomiting, chest pain and diarrhea. The maximum allowable chlorine content in 1L air is .1mg, which will cause human poisoning.
Extended information:
1. Discovery of chlorine
Scheler discovered chlorine in 1774, when he was studying pyrolusite (manganese dioxide). When he mixed pyrolusite with concentrated hydrochloric acid and heated it, he produced a yellow-green gas. The strong pungent smell of this gas made Scheler feel extremely uncomfortable, but when he was sure that he had made a new gas,
After Scheler prepared chlorine gas, it was dissolved in water, and it was found that this aqueous solution had permanent bleaching effect on paper, vegetables and flowers. He also found that chlorine can react chemically with metals or metal oxides. From Scheler's discovery of chlorine in 1774 to 181, many scientists have studied the properties of this gas.
during this period, chlorine gas has always been regarded as a compound. It was not until 181 that David confirmed that this gas was a substance composed of a chemical element after a lot of experimental research. He named this element chlorine, which comes from Greek and means "green". In China's early translation, it was translated as "green gas" and later changed to chlorine gas.
2. History of technical development
The production method of chlorine gas has experienced a long development process. In 1774, Swedish chemist Scheler reacted pyrolusite (containing manganese dioxide) with concentrated hydrochloric acid to first produce chlorine gas. The reaction equation is:
4HCl (concentrated) +MnO? = heating = MnCl? +2H? O+Cl?
however, because hydrochloric acid could not be produced in large quantities at that time, this method was limited to the production of chlorine gas in the laboratory. Later, French chemist Bertole put the mixture of sodium chloride, pyrolusite and concentrated sulfuric acid into a lead distiller, and after heating, chlorine gas was produced. The reaction equation was:
2NaCl+3H? SO? (concentrated) +MnO? = heating =2NaHSO? +MnSO? +2H? O+Cl? ↑
Because the raw materials of this method are easily available, people have been using the method of Berto Lei Faming to produce chlorine from 1774 to 1836.
In p>1836, Gusag invented a coking tower to absorb sodium carbonate (Na? CO? ) in the process of hydrogen chloride gas (previously this kind of gas containing hydrogen chloride was considered as a kind of waste gas, and it was fully utilized from Gusag) to get hydrochloric acid.
Since then, hydrochloric acid has become a relatively cheap acid, which can be widely used. The method of producing chlorine invented by Scheler has been improved, and only then has it become a method of producing chlorine on a large scale.
in p>1868, Dickon and Hont Hungary invented the method of using copper chloride as catalyst, and using oxygen in the air to oxidize hydrogen chloride gas to produce chlorine gas when heating. The reaction equation is:
4HCl+O? =2H? O+2Cl?
this method is called Deakin method. (also translated as Dikang method)
Although these methods for producing chlorine have played a certain role in history, they are greatly inferior to those for producing chlorine by electrolysis in terms of economic benefits and production scale. When electrolysis is put into practice, these methods for producing chlorine are gradually eliminated.
the birth of electrolysis dates back to 1833. After a series of experiments, Faraday found that chlorine can be obtained when current is applied to the aqueous solution of sodium chloride. The reaction equation is:
2NaCl+2H? O ==2NaOH+H? ↑+Cl?
Later, the British scientist Watt also discovered this method, and in 1851, he obtained a British patent on the production of chlorine gas. However, because there was no practical DC generator to generate enough current at that time, the electrolysis method could only stay in the laboratory scale and could not be put into industrial production, so it was shelved.
it was not until the 197s and 198s that relatively good DC generators appeared, and electrolysis was widely used. Since then, the industrial production of chlorine has entered a new era. However, at that time, the electrode used to produce chlorine gas by electrolysis was mercury, which led to a considerable amount of mercury vapor mixed in chlorine gas and hydrogen gas obtained by electrolysis.
This "chlorine production by mercury" is very harmful to the environment, so the new "ion exchange membrane method" is more environmentally friendly and energy-saving. (Chlorine production by mercury is the mainstream method to produce chlorine gas, for example, 46% of chlorine gas was produced in China in 21 and 5.1% in Western Europe in 2).
Reference: Baidu Encyclopedia-Chlorine.