The Discovery of the Periodic Table.pdf (original) (raw)

This paper conducts a study of the History of Chemistry from the Phlogiston Theory to the Periodic Table. It traces the changes and new discoveries made in chemistry from the 18th century to the second half of the 19th century. It examines the chemical revolution of the late 18th century, the discovery of new elements and theories, which eventually led to the development of the periodic table. It concludes by an analysis of the order of the discoveries made in chemistry during that period. It notes that many of the discoveries had to occur in a particular order and that the order of those discoveries was inevitable. This is a conclusion consistent with that stated in my website How Change Happens: A Theory of Philosophy of History, Social Change and Cultural Evolution. A new scientific attitude had begun to appear in Europe in the 16th and 17th centuries but this had little effect on chemistry until the 18th century. In the 18th century methods for the qualitative and quantitative analysis of minerals improved resulting in the discovery of new compounds and elements. The blowpipe became a common laboratory tool while the practice of weighing precipitated salts was introduced by Torben Bergman when analyzing mineral waters. This practice was improved by Klaproth who heated the salts to dryness before weighing them, which produced more accurate results. Klaproth also began the practice of reporting the actual percentage composition, as produced by his analysis, regardless of whether it totaled 100% and this allowed the discovery of errors in analysis and to the discovery of new elements in the materials analyzed. The new laboratory methods led to the discovery of new elements such as cobalt (1735), platinum (1740-1741), zinc (1746), nickel (1754), bismuth (1757), manganese (1774), molybdenum (1781) tellurium (1782), tungsten (1785) and chromium (1798). The oxides of zirconium, strontium, titanium and yttrium were also discovered. Many of the new substances were metals and this led to the demise of the ancient doctrine of seven metals. In the second half of the 18th century Carl Scheele discovered hydrofluoric acid and the compounds hydrogen cyanide, lactic citric and malic acids and glycerol. The phlogiston theory was introduced by Becker and Strahl in the late 17th and early 18th centuries. The theory considered all combustible substances contained phlogiston which was lost to the air during the process of combustion. A limited amount of air could only absorb a limited amount of phlogiston, which explained why combustion ceased, if only a limited amount of air was available. Combustion would also cease as soon as substances ran out of phlogiston. The phlogiston released into the air was absorbed by plants, which were eaten by animals, so that the phlogiston was recycled into known combustible materials.