1. Law and Chaos (1640-1665) CM1100 History of Chemistry: Gases and the Gas Laws

2. Ancient Beliefs Matter made up of 4 ELEMENTS: Air, Earth, Water, Fire. 4 Qualities: Hot, Cold, Moist, Dry Nature abhors a vacuum Aristotle

3. Galileo’s Laboratory (1638-43) Galileo had questioned why a suction pump could only raise water in a mine by about 9-10 metres. Torricelli, his secretary, proposed an experiment performed by Viviani in 1643 (after Galileo was dead) to prove that the effect was caused by atmospheric pressure. Nature does not abhor a vacuum!

4. Weight of the Atmosphere Viviani took a 2.5m long glass tube and filled it with mercury and inverted it into a bowl of mercury. Mercury is 13.6 times denser than water and the mercury column rose to about 76 cm. A vacuum was created at the top of the tube

5. The Barometer (Gk “baros” for weight; “metron” for measure) The column of mercury rose and fell depending on the weather The weight of the column of mercury was equal to the weight of the air The type of experiment had been performed with water some years before in Rome

6. Pascal and Périer (1648) Torricelli wrote a letter explaining his findings on atmospheric weight. It eventually reached Blaise Pascal in France. He instructed Florent Périer, his brother in law, to make measurements with a mercury barometer at the bottom and top of Puy de Dome (an extinct volcano, 1.5m high) in the Massif Central The experiment showed that the pressure of the atmosphere decreased with height.

7. van Helmont (1579-1644) [yet another famous Belgian!] He believed that Air was the basis of all matter He coined the word GAS (Gk “khaos” for empty space) as the product of some chemical reactions e.g charcoal burning

8. Gas Sylvestre (Gas from Wood) We know this gas today as CARBON DIOXIDE. van Helmont’s work (published after his death in 1648) indicated that it was produced not only from burning charcoal but also from spa water, fermenting wine and eructions.