“The Activity of the Individual Ions in Aqueous Solutions. Are they Real or Imaginary?”
Abstract
For more than eighty years it was not only said but repeated continuously that it was not possible to measure the activity of individual ions in aqueous solutions.
This was the commonly accepted paradigm. A few researchers, not more than three, were brave enough to publish electrochemical measurements from which such activities could be obtained.
They published their results either with apologies indicating their understanding that there was no theoretical support for their claims or calling the results “a convenient scale of ionic activities”.
When we, at McGill University, figured out that there were commercial ion selective electrodes to measure the mean ionic activity coefficients of electrolytes in aqueous solutions, we reasoned that from the response of the ion selective electrode of each of the two individual ions of a salt, we could obtain information on the activity of the individual ion.
As many well-established researchers were against this concept, we had a hard way to go. If anyone had taught students or published statements in a book according to the existing paradigm, it was too much to ask them to change their mind now.
Graduate students need to have their PhD Thesis approved to find a job. Thus, that we could never sacrifice any of them by giving this topic as a graduate research project and risking the rejection of the thesis. Hence, all the work done measuring the activities of individual ions was done either with postdoctoral students or visiting scientists.
This talk will tell the story of a difficult path when one attempts to change a paradigm and prove that you can do what you believe you can do.