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I have the formulae:
P'= (A2 x Vw)/((A1-A2)xVo)

and P/P' = 1 + K[I-]w

where: Vo is the vol of the organic layer
          Vw is the vol of the aqueous layer
          P and P' are the partition coefficients
         [I-]w is the conc of iodine in the aqueous layer
          And A2 and A1 are the absorbances I have determined spectroscopically.

20cm3 of I2 in DCM solution was shaken with 1500cm3 of water, and the aqueous layer decanted and the absorbance found. SO A1= 1.977 and A2=1.565.
I need to find P. But do I use 1500 as the Vw and 20 as the Vo? Or does it have to be the volumes after the extraction? In which case the vol of the organic layer was 5cm3, so does that mean the vol of the aqueous would be 1515???

So: P= (1565x 1500)/ ((1.977-1.565) x20) = 284.9
Is this an accurate answer?

And then I have to use the same method to find out P when I2 in DCM is shaken with varying vols of KI, and then find K.

Any help would be great thanks!