I am trying to understand some of the historical context behind the discovery of atoms (pre-Avogadro). In particular, I am getting stuck in reading the following documents:
My understanding is that "atoms" (as they understood them at the time) were discovered to react in whole-number ratios by Proust/Dalton/Berzelius (who measured by mass) and by Gay-Lussac (who measured by volume). While this was highly suggestive of some sort of "atom" concept, there was a discrepancy between the two sets of measurements. But I'm having trouble following the specific discrepancy pointed out by the above PDFs.
The first PDF gives the following mass data:
Mass of Nitrogen Mass of Oxygen Nitrous Oxide (N₂O) 100 g 58 g Nitric Oxide (NO) 100 g 127 g Nitrogen Dioxide (NO₂) 100 g 239 g
The text doesn't explicitly mention how this data was interpreted by Proust/Dalton/Berzelius. Looking at the data, I don't see that much can really be said:
? N + 1 O = ? Nitrous Oxide (N₂O) ? N + 2 O = ? Nitric Oxide (NO) ? N + 4 O = ? Nitrogen Dioxide (NO₂)
The question marks are there since they didn't know what was "in" 100 g of nitrogen, which would mean that they didn't really know what was in the product, either, right?
So that's my first question: Am I correct in thinking that the above is about as far as Proust/Dalton/Berzelius could go with that data? Or were they pretty sure they knew how to fill in the question marks?
Now, continuing on to the second PDF, when Gay-Lussac measured by volume, he had:
Volume Nitrogen Volume Oxygen Volume Product Nitrous Oxide (N₂O) 100 49.5 100 Nitric Oxide (NO) 100 108.9 200 Nitrogen Dioxide (NO₂) 100 204.7 200
Now, the document goes on to say that the above data might suggest the following formulas:
2 N + 1 O = Nitrous Oxide (N₂O) 1 N + 1 O = Nitric Oxide (NO) 1 N + 2 O = Nitrogen Dioxide (NO₂)
The text then says that the equation for nitrous oxide represents a contradiction.
But I don't see how that contradiction follows from the data. As the text suggests, if we say that a volume of "50" represents one "atom" (so that volume of "100" nitrogen represents two atoms), wouldn't we say:
2 N + 1 O = 2 Nitrous Oxide (N₂O) 2 N + 2 O = 4 Nitric Oxide (NO) 2 N + 4 O = 4 Nitrogen Dioxide (NO₂)
Wouldn't that mean really it's the other two equations that don't make sense based on the number of atoms not working out? I feel like I'm missing a basic idea in the text.
(FYI, I am not in school and so I'm not a student, nor is this homework.)