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There is an ancient inventio...

There is an ancient invention still used in some parts of the world today that allows people to see through walls. What is it?

Correct answers: 49

The first user who solved this task is Djordje Timotijevic.

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Carl Wilhelm Scheele

Died 21 May 1786 at age 43 (born 9 Dec 1742). (also Karl) Swedish chemist who discovered oxygen in 1772. Scheele, a keen experimenter, worked in difficult and often hazardous conditions. In his only book, Chemical Observations and Experiments on Air and Fire (1777), he stated that the atmosphere is composed of two gases, one supporting combustion, which he named "fire air" (oxygen), and the other preventing it, which he named "vitiated air" (nitrogen). Due to delay in his publication, he lost priority to Priestley's discovery of oxygen in 1774. Scheele discovered many substances, such as chlorine (1774), manganese (1774), tungsten (1781), molybdenum (1782), glycerol, hydrocyanic (prussic) acid, citric acid, hydrogen sulphide and hydrogen fluoride. He also discovered a process resembling pasteurization.

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