As part of my coursework I have conducted an experiment to find the partition coefficients of various organic solutes in organic and aqueous solvents.
The equation I used was Log10([Solute in solvent A] / [Solute in solvent B])
This gave me results which matched the prior research I had conducted. Partition coefficients above 1 corresponding to a solute which favours an organic environment and vice versa. For example a coefficient of 1.2 shows that for every 1.00 moldm-3 of solute in solvent B there is 1.20 moldm-3 of the solute in solvent A.
My problem arose when I had two concentrations which were very close in value. 6.38x10-3 moldm-3 in Solvent A and 6.33x10-3 moldm-3 in Solvent B. I assumed that the partition coefficient of these two concentrations would give a result around 1, as they are nearly equal. But inputting the concentrations into the equation above gave me a partition coefficient of 3.42x10-3, which corresponds to a greatly hydrophilic solute and doesn't make sense given the close to equal concentrations.
For another set of concentrations which were fairly equal, 6.00x10-3 moldm-3 and 6.13x10-3 moldm-3 , the results were even more strange. A partition coefficient of -9.31x10-3 which shouldn't be a possible value.
What is going on here and is there some other way i can calculate partition coefficients without these wild results?
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