Dr. Stephen Lukacs (May 2012)
One of the most simple chemical instruments known; apply a voltage across a liquid solution and measure the induced current through the solution, called conductivity. The more ions, the greater their mobility, the greater the current and respective conductivity. The molecular model of the experiment is a bit more complicate then expected, especially at higher concentrations of ions. I wonder why?
(May 2012) The written lecture and mathematical models fitted to the experimental data.
(May 2012) This podcast overviews the calibration process; making standards volumetrically, testing those standards, fitting the data to an appropriate physically-relevant model, and then solving for that equation in order to accurately report unknown samples.
(May 2016) Shows how to do the lab and mainly how to do serial dilutions necessary for making proper standards/knowns for instrument calibration.
Don't forget to fit your data to the form of the Conductivity Equation, or:
L = a C3/2 + b C + c
where L is the microSeimens reading from the probe, C is the known concentration of your standard serial dilutions of potassium chloride, and a, b, and c are your fit parameters. Besides fitting the equation, you'll have to numerically calculate the concentrations of the various unknown solutions of water using Goal Seek in Excel because you can not analytically solve for L using this equation.(May 2016) You can easily fit lines in Excel using linest or trendlines in a scatter plot. Forcing Excel to fit more complicated functions requires more effort and more learning. This spreadsheet has two examples of fitting the conductivity's 3/2 polynomial to some sample data. The file contains two tab sheets with two different methods of doing this in Excel.
(June 2012) Conductivity is an excellent and efficient method for standardizing NaOH base solutions, for use in acid/base titrations. This PDF outlines exactly how to gather the data and find the equivalence/endpoint.