Chemistry (History Of Salt)
...were on the earth. Sodium chloride was being used before written history began. 2,700 years B.C there was published in China the Peng-Tzao-Kan-Mu, probably the earliest known pharmaceutical guide. (Sodium) A major part of this writing was devoted to a analysis of more than 40 kinds of salt, including descriptions of two methods of extracting sodium chloride and putting it in a usable form that are very much like our processes today.
Egyptian art from as long ago as 1450 B.C. records salt making. A couple of more recent examples are drawings of a 15th century French salt evaporation plant, a 16th century Persian picture of a Kurdish salt merchant and a 17th century Italian print offering instructions in distilling salt.
(N.N.) Salt was of very important economically. A trade in Greece involving exchange of salt for slaves made the expression, "not worth his salt." The Romans were good builders of salt works as well as other vital infrastructure. Special salt rations given early Roman soldiers were known as "salarium argentum," the forerunner of the English word "salary." References to salt abound in languages around the globe, particularly regarding salt used for food. Until the 18th century, there was no distinction made between potassium and sodium. This was because early chemists did not recognize that "vegetable alkali" and "mineral alkali" are distinct from each other. Eventually a distinction was made. (Sodium) Sodium was first isolated in 1807 by Sir Humphrey Davy, who made it by the electrolysis of very dry molten sodium hydroxide, NaOH. Sodium collected at the cathode. Shortly after, Thenard and Gay-Lussac isolated sodium by reducing sodium hydroxide with iron metal at high temperatures. Sometime prior to the autumn of 1803, the Englishman John Dalton was able to explain the results of some of his studies by assuming that matter is composed of...
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