Daltons Concepts on Elementary Molecules, by Avogadro

The Dalton s atomic theory was immediately faced with molecular samples as stated by Avogadro (1811)  

On the other hand, there is more likely that the molecules of gases being at such a distance, their mutual attraction cannot be exercised, their attraction varying for caloric measure could be limited to the atmosphere 

Dalton, proposed a direct hypothesis (opposed to this one) the caloric quantity is always the same for the molecules of all bodies, whatever the aggregation state is, and the more or less is the attraction for caloric sample it only leads to a greater or a smaller condensation production of this quantity around the molecules, thus varying the distance between the molecules themselves. There was no evidence helping to decide in favor of one of these theories, therefore, one has been inclined towards a neutral hypothesis, according which the distances between molecules and caloric quantities vary according to unknown laws, which is not the case of the presented hypothesis, i.e., based on the simplicity of the relationship between the gases volumes in combination, which otherwise seem inexplicable. 

Quantum Nanochemistty—Volume II Quantum Atoms and Periodicity 

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