John Kudrysch History of Chemistry
Help Received: Leicester Book
The laws of atomic combination are already known to us but in the late 18th, early 19th, century Benjamin Richter was the man to revolutionize how we today see chemical reactions in their entirety. Stoichiometry was not a known aspect of chemistry, but Richter coined the term and showed through his notes of experimentation that it was possible to realize what was being formed if the initial compounds were known (1). So, in essence he proved that AB and CD added together will yield AC and BD, but if the initial compositions of AB and CD were known then AC and BD could also be calculated (1). This was breakthrough, but unfortunately for his time his work did not influence the time he lived in because of all the mathematical relationships he was trying to prove through this method (1). Dalton came up with a theory where he organized atoms into circles, and gave them symbols or shaded them differently to represent each element he wanted to work with (1). This allowed him to visually show his idea how he believed atoms interacted and bound together to create different compounds. Water, for example, would have hydrogen and oxygen in it since at that time both elements were proven to exist as water together (1). This, however, was unrefined and underdeveloped. Dalton never really changed his theory but the concept allowed for future chemists to build off of it and gradually come to the truth that we now know (1). The first part of the 19th century allowed for an observation of elements unlike previous years. Here we have quantitative properties of compounds, possible accurate relationships between compounds expressed, and the identification of elements and compounds as separate entities (1).
(1). H.M. Leicester. The Historical Background of Chemistry, Dover Publications Inc, New York, USA, (1956) pp. 150-164