THE GROWTH OF CHEMICAL IDEAS 121 



bustion was due to a combination of the material with oxygen. 

 In 1789, the year of the French revolution, Lavoisier pub- 

 lished the work on which all chemistry is founded today and 

 freed the chemical world from its obsession with the phlo- 

 giston theory, which had delayed its progress for so long. 



All the early work in chemistry had been concerned with 

 the nature of reaction, and after the experiments of Lavoisier, 

 which elucidated the properties of oxygen and its reaction 

 with hydrogen, carbon, and other elements, rapid progress 

 was made toward understanding not merely the nature of 

 reactions but the quantitative laws which govern them, so 

 that the principles of quantitative analysis could be laid 

 down. As a result of this, J. L. Proust, a French chemist who 

 was director of the Royal Laboratory in Madrid, was able to 

 show that a definite chemical compound always contains the 

 same elements combined in the same proportions by weight. 

 This law of definite proportions was the basis on which 

 Dalton founded his atomic theory. 



John Dalton was a teacher of mathematics, physics, and 

 chemistry, chiefly in Manchester, but, as he says in his brief 

 biography, "occasionally by invitation in other places; 

 namely, London, Edinburgh, Glasgow, Birmingham, and 

 Leeds." Dalton considered Proust's law of definite propor- 

 tions and concluded that chemical compounds are formed by 

 the combination of certain unit weights of the elements. The 

 smallest possible unit he termed an atom, following Lucre- 

 tius; and he concluded that the atoms of the elements must 

 vary in weight, these atomic weights being basic physical 

 properties of the elements. 



Jons Berzelius was the organizer of the science of chem- 

 istry. He was a medical man, teacher, and finally a professor 

 of chemistry at the College of Medicine at Stockholm. He 

 introduced the system of chemical nomenclature, of the 

 symbols for the elements and formulae for compounds, and 

 he developed great skill in chemical analysis, as a result of 

 which he determined the atomic weiofhts of the elements 



