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Shiavault - a Vault of Shia Islamic Books The Roots of Religion Lesson 6: Lavoisier’s Law and Creation We have all seen names of fire, and we recognise what they are, but when we see these flames soaring up do we ever stop to ask what in fact they are. Today we know that flames are composed of gases combined with oxygen from the air.

But, previously some chemists had thought that there was some invisible substance in charcoal and oil which, when there is ignition, is released in the form of flames. To this substance they gave such names as “sulphur” This idea gathered many supporters, and many scientists subscribed to it, calling this invisible substance “phlogiston”. George Ernst Stahl; German scientist, chemist and biologist, who, in 1694, became professor at Hall University. (b. 1660, d.

1734.said that phlogiston was a substance, which escaped and which was the basis and essence of fire; that it was hidden inside inflammable materials; and that at the time of burning it was released in the form of flames. He said that the reason that wood, charcoal and oil burn readily is that there is more phlogiston in them, but that in metal there is less of it.

He and other followers of this idea believed that in the combustion of iron, phlogiston was released and what remained took the form of rust. They also said that when sulphur was burnt, phlogiston was released, and a colourless gas remained which was sulphur without phlogiston. Rouelle [French scientist (b. 1703. d. 1770) a great chemist and the tutor of Lavoisier, also accepted this theory, and tried very hard to prove it.

Lavoisier, the French scientist, one of the founders of modern chemistry, researched into what his teacher, Rouelle, and other scientists had said, spending much time thinking about their theory, until he realised that the belief in phlogiston was groundless. In 1772, he effected the combustion of a piece of lead by focusing the rays of the sun on to it by means of magnifying lenses. He observed that its weight increased.

He deduced that some part of the air had become combined with the metal and had added to its weight: if phlogiston had been there, the weight of the lead would have decreased. Thus, he claimed, the phlogiston theory should be abandoned. In support of his view he asserted that if the 'burns' lead were heated it would return that part of the air which it had taken, and would again become lead.

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