After an apprenticeship as a pharmacist, Bernard joined his father's business. Iodine was discovered by Bernard Courtois (1777-1838) who learned the manufacture of saltpeter from his father. Because many oxides are in fact acidic, discarding the explanation that oxygen causes acidic properties was unreasonable for many chemists. muriatic acid (HCl), lacking any oxygen, would require a new explanation for acidic properties. Davy proposed the name Chlorine (Cl = #17): Khloros (Greek) for yellow green because the gas is that color. After other attempts to release oxygen failed, Davy concluded that dephlogisticated muriatic acid gas was actually an element rather that a compound with oxygen. In 1808 Humphry Davy decomposed muriatic acid with potassium producing hydrogen and potassium chloride. Claude Berthollet, a colleague of Lavoisier, therefore proposed that Scheele's dephlogisticated muriatic acid gas must be a combination of oxygen and an undiscovered element, muriaticum. Lavoisier named the gas responsible for combustion oxygen, meaning acid forming, because all compounds containing oxygen seemed to be acidic. Meanwhile in Paris a friend of Fourcroy and Vauquelin, Antoine Lavoisier, proposed to replace both the four element theory and phlogiston with numerous new elements and a concept of combustion involving a new gaseous element. Believing that pyrolusite had removed phlogiston from muriatic acid, Scheele named this air dephlogisticated muriatic acid. Like most chemists of the time, Scheele subscribed to the phlogiston theory which attempted to explain chemical reactions. He noticed that this air dissolved slightly in water, imparted an acid taste, bleached flowers and leaves, and attacked all metals. Among other discoveries, he noted that when he let finely ground pyrolusite (MnO 2) stand with the spiritus salis (also called muriatic acid) it produced a suffocating odor like warm aqua regia, most oppressive to the lungs. Bergman suggested the problem to his friend Carl Scheele (1742-1786 shown at right) who in 1774 reported three years of experiments on pyrolusite. Bergman thought the mineral, also called magnesia nigri, was the calx of a metal but he was unable to isolate the metal. Pyrolusite was a half mineral which had been used for centuries to give a violet color to glass and pottery. Vauquelin, and Klaproth in Germany, became the top analytical chemists of their day. Vauquelin later became inspector of mines and professor of assaying at the School of Mines where he continued to live under the care of the Fourcroy sisters until their deaths. Because of the many colors of its compounds, Fourcroy and Haüy suggested the name Chromium(Cr = #24): Khroma (Greek) for color. Upon cooling he discovered a network or gray, metallic needles weighing 1/3 the original. In 1798 he precipitated lead with muriatic acid, dried the green solid, then cooked it for half an hour in a charcoal crucible with charcoal dust. Adding tin muriatic turned the solution green. The solution formed a beautiful red precipitate with a mercury salt, and a yellow precipitate with lead. Vauquelin boiled pulverized crocoite with two parts potash obtaining a yellow solution. Because of the French Revolution, Vauquelin left Paris in 1793, served as pharmacist in a military hospital, then returned to teach chemistry at the Central School of Public Works which later became the École Polytechnique. Vauquelin continued to rapidly learn physics, chemistry and philosophy while assisting Fourcroy with chemistry and the teaching of Fourcroy's students. Vauquelin lived with Fourcroy and his unmarried sisters who provided motherly care. Hearing of Vauquelin's interest in chemistry, Fourcroy hired the boy as his assistant. One pharmacy was owned by a cousin of the chemist, Fourcroy. He went to Paris with a letter of introduction and worked for several apothecary shops. ![]() Vauquelin was born to a farm laborer in Normandy, made rapid progress in school, and at age 14 became a dishwasher and assistant in an apothecary. In 1797 Nicolas-Louis Vauquelin (1763-1829 shown at left), noting its beauty, scarcity, value equal to gold, and several contradictory chemical analyses, determined to find the correct composition of crocoite. He died the next year when a retort containing arsenic burst upon heating. Johann Gottlob Lehmann investigated this mineral known as crocoite or crocoisite in 1766 and found it produced an emerald-green solution when dissolved in muriatic acid. Small amounts of a red mineral were obtained accompanying lead ore. The four Siberian Beresof gold mines had been worked for gold, copper, silver and lead since 1752.
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