Man's physical universe



The Quantitative Nature of Chemical Changes Was Demonstrated by


The atomic hypothesis remained a mere valueless speculation until

the quantitative nature of chemical changes had been established.

Bergman (1735-1784), Joseph Black (1728-1799), and Henry Cavendish

(1731-1810) all made use of the balance in the study of chemical

processes; but it is to the brilliant French chemist, Antoine Lavoisier

(1743-1794), that is due the credit for introducing the quantitative

epoch in chemistry. Until chemical changes were studied quantitatively,

there was little opportunity for real progress, so Lavoisier is

usually called the "father of modern chemistry."

Antoine Laurent Lavoisier was born in Paris and early showed a

great aptitude in scientific investigation, especially in chemistry. He

made many practical contributions of importance, such as the improvement

of gunpowder. Lavoisier's most important contribution was the

introduction of the balance into chemical investigations. With its aid

he overthrew the erroneous phlogiston theory of combustion, which

assumed that whenever a substance was burned there was lost from

that substance a mysterious "phlogiston." Lavoisier showed that

combustion is really a combination of oxygen with a substance.

In 1789 Lavoisier advanced the law of the indestructibility of matter,

or what is now known as the law of conservation of mass. This law

simply states that there is no perceptible gain or loss in weight in any

chemical change.

In 1793 Lavoisier met his death on the guillotine.

Despite his great

services to his country, the fact that he was a member of the aristocracy

and had been associated with a hated tax-collecting company

caused him to be sentenced to death by the French revolutionists.

C. S. Minot said of this event: "Compared with the growth of Science,

the shiftings of Governments are minor events. Until it is clearly

recognized that the gravest crime of the French Revolution was not the

execution of the King but the execution of Lavoisier, there is no right

measure of values; for Lavoisier was one of the three or four greatest

men France has produced."

Other Quantitative Laws of Chemical Reaction Were Soon Discovered.

The labors of many investigators in the years just following the

death of Lavoisier established a second law of chemical change which

was quantitative in nature, just as was Lavoisier's law of conservation

of mass. This second law, called the law of definite composition, stated

that the composition of a chemical compound is definite in nature; i.e.,

is always composed of the same elements in the same proportions by weight.


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