Gay-Lussac and Avogadros Hypothesis

Dalton s work provided a system for representing chemical reactions, but inevitably, conflicts arose when trying to resolve Dalton s idea on chemical combination with experimental evidence. According to Dalton, one volume of nitrogen gas combined with one volume of oxygen to give one volume of nitrous gas (nitric oxide). Dalton referred to combination of atoms as compound atoms. Using Dalton s symbols, this reaction would be represented as 

1 nitrogen atom +1 oxygen atom gives 1 compound atom of nitrous gas 

But when one volume of nitrogen reacted with one volume of oxygen, the result was two volumes of nitrous oxide, not one. Joseph Louis Gay-Lussac (1778-1850) had experimentally demonstrated that two volumes of nitrous gas result from combining one volume of nitrogen with one volume of 

1 molecule of nitrogen + 1 molecule of oxygen gives 2 molecules of nitrous gas 

Avogadro had no experimental evidence to back his claim, yet his hypothesis solved the problem. It took fifty years for the scientific 

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