http://www.primeonlinetutor.com/cd3 Acids have been used and studied for hundreds of years. Over time their definitions have been refined. The original definitions of acids and bases were based on their observed properties. Early chemists noticed that solutions of some substances had a sour taste, so they called them acids after the Latin word acidus, meaning sour. Solutions of some other substances tasted bitter and felt greasy. As most of these were made from the ash residue of burnt plants, they were called alkalis after an Arabic word for heated ashes. Antoine Lavoisier (1743-1794) is sometimes called the father of chemistry. Lavoisier was a French chemist who showed the importance of accurate measurements, demonstrated that combustion involves reactions with oxygen and wrote the first modem chemistry textbook. His experiments on combustion led him to believe that acids were made of two substances: oxygen, which causes acidity and is common to all acids, and another substance that is unique to each acid. Sir Humphry Davy (1778-1829) was an English chemist. He is famous for his experiments on electrolysis, the discovery of a number of elements and for showing that all acids do not contain oxygen. In 1810, Davy proved that muriatic (hydrochloric) acid does not contain oxygen but is a compound of hydrogen and chlorine. During the next 20 years, at least 10 more acids that do not contain oxygen were discovered. He proposed that acids contained replaceable hydrogen atoms as hydrogen was evolved when acids attacked metals. In 1884 a Swedish chemist, Svante Arrhenius (1859-1927) suggested the following theory of acids and bases. CD3411 http://youtu.be/KGzDZRqiVyI

• published: 18 Nov 2013
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