Hello! In one of my laboratory classes in college, I tried experimental determination of salicylic acid's lipossolubility (LogP). I dissolved it in octanol, read the absorbance at 668nm (A0), and added in the same volume of water, and mixed it again. After half an hour, I separated the organic phase and read the absorbance again (Ax).

Everything seemed to go well until I noticed Ax was bigger than A0, which would mean the acid concentration had somehow increased (from 135 to 255). This is impossible since we didn't add any more acid since the first read; the value should have decreased because some of it should have gone to the aqueous phase.

I have to submit a report and after some research I still can't imagine why the damn value increased. Any thoughts?