Composite 8 -14

Composite 8 -14 - Chemical Principles Calxes and Airs...

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Chemical Principles, Calxes and Airs Different species of airs? Called gases Airs can be fixed in solids – Lavoisier’s work on combustion o Travels to eastern France with geologists to determine which kinds of mineral resources might be available in eastern France Aristotle elements: earth air fire water o Are these just states of matter? The production of air from earth o Really interested in the physical aspects of the production of fixed air o How was it possible for air to become fixed from solid matter in the first place? (Lavoisier) o Air in its usual state consists of air particles associated with air surrounded by an atmosphere, or cloud of very supple fire particles o Each of these air particles with this cloud of fire particles surrounding it forces all of the air particles to push each other apart because of the fire particles o When the air particles were not surrounded by fire particles, they were not aerial, and became fixed air in solid matter o Fire consists of heat particles o If you have a lump of matter and you heat it up , what you are actually doing is introducing fire into that lump of solid matter. The fire particles enter and combine with the fixed air particles which are already in the solid matter, releasing the air particles into the atmosphere. o Calcination reactions: forming calx from metal by burning it The resulting calx weights more than the initial sample of metal with which you started in lead and tin?/! They were ignored, something weird was happening If combustion was the loss of phlogiston, then you would expect that what was left behind would always weigh less. The phlogiston was driven off! Lavosier does weight trial studies Tries phosphorus with a nicely sealed reaction vessel
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He finds that the solid material gains quite a lot of weight Same thing with sulfur In both cases, it seems to Lavosier that a lot of air has been used up as well This increases his suspicion that air is somehow being used up and absorbed into the solid matter as a result of combustion Then he tries to reverse the process There must be air in the calx! Try and get air out of the calx! He uses a pneumatic trough apparatus to try and produce air from the calx He heats the lead oar (a calx) in a vessel in the presence of charcoal He then observes a large amount of air bubbling up into the apparatus as the lead oar turns into metallic lead. And then when the metal is completely reduced back to the metal, the bubbles stop coming off. This reinforces his idea that what is going on there is that the air which has been absorbed into the calx is released again when you reduce the oar back to the metal at the end of 1772 1774 and 1775: o oxygen theory of combustion o By 1774 Lavoisier decided that combustion was the fixing of air into metals Lavoisier and “elements” The release of “fixed Air” and the matter of fire The weight of Calxes Guyton de morveau (1772)
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Composite 8 -14 - Chemical Principles Calxes and Airs...

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