Actually if I understand correctly scientists in the 1700's and 1800's understood ideas like "combining ratios" that were antecedents to modern chemistry. So, they'd know that 2 parts hydrogen 1 part oxygen was water, etc, long before they understood the structure of the atom (which was Rutherford in 190x).
Spats_McGee t1_j9ckytw wrote
Reply to comment by VT_Squire in How did we first figure out which substances are elements and which are compounds? by sapphics4satan
Actually if I understand correctly scientists in the 1700's and 1800's understood ideas like "combining ratios" that were antecedents to modern chemistry. So, they'd know that 2 parts hydrogen 1 part oxygen was water, etc, long before they understood the structure of the atom (which was Rutherford in 190x).