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реферирование английского текста онлайн1. science plays such an important part in the modem world that no one can now feel that he understands the world in which he lives unless he has an understanding of science.the science of chemistry deals with substances. at this point in the study of chemistry we shall not define the word substance in its scientific sense, but shall assume that you have a general idea of what the word means. common examples of substances are water, sugar, salt, copper, iron oxygen — you can think of many others. nearly two centuries ago it was discovered by an english chemist, sir humphry davy 1778 1827 , that common salt can be separated, by passing electricity through it, into a soft, silvery metal, to which he gave the name sodium, and a greenish yellow gas, which had been discovered some time earlier, and named chlorine. chlorine is a corrosive gas, which attacks many metals, and irritates the mucous membranes of the nose and throat if inhaled. the discovery that the properties of common salt are quite different from those of sodium or chlorine is one of the many surprising facts about the nature of substances that chemists have found out. a sodium wire will burn in chlorine, producing salt, the process of combination of sodium and chlorine to form salt being called a chemical reaction. when a mixture of gasoline and air explodes in the cylinders of an automobile a chemical reaction takes place, and at the same time the energy is released to move the automobile. both carbon dioxide and carbon monoxide are compounds of carbon and oxygen, and water being a compound of hydrogen and oxygen. 2. chemists study substances to learn as much as they can about their properties their characteristic qualities and about the reactions that change them into other substances. knowledge obtained in this way has been found to be extremely valuable. since some substances like morphine and cocaine , may have undesirable properties along with the positive ones, we should test such substances for their powers of deadening pain and of producing addiction very thoroughly. in the beginning, some methods carried out in laboratories were really dangerous, e.g. a young investigator, h. davy tested many gases on himself by inhaling them. he discovered that one gas named laughing gas ,produced a state of hysteria when inhaled, and that people seemed not to suffer pain when they fell down or bumped into an object. it is rather surprising, but that gas was not suggested to be used in surgical operations right after its discovery. no one seems to have had this idea, and the use of anesthetics was delayed for nearly half a century. then another investigator in the united states noticed that the chemical substance ether, when inhaled, produces unconsciousness, and another one noticed the same effect with chloroform. these substances were soon brought into general use. the discovery of anesthesia was a great discovery, not only because it relieves pain, but also because it permits delicate surgical operations to be carried out that would be impossible if the patients remained conscious.no doubt that the twentieth century may be called the chemical age.
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